diff --git a/docs/Nodes-threads-locks-links.md b/docs/Nodes-threads-locks-links.md
index 1f2a9dd..8108168 100644
--- a/docs/Nodes-threads-locks-links.md
+++ b/docs/Nodes-threads-locks-links.md
@@ -119,7 +119,7 @@ We don't currently have any other mutable objects, but in future at least lazy o
 
 Secondly, reading from a namespace does not happen in a single clock tick, it takes quite a long time. So it's no good setting a lock bit on the namespace object itself and then immediately assuming that it's now mutable. A reading process could already have started, and be proceeding.
 
-So what I think is, that we have a single top level function, `(::substrate:search-store key store return-key?)` (which we already sort of have in the 0.0.6 prototype, [here](https://www.journeyman.cc/post-scarcity/doc/html/intern_8c.html#a2189c0ab60e57a70adeb32aca99dbc43)). This searches a store (hashmap, namespace, association list, or hybrid association list) to find a binding for a key, and, having found that binding, then, if there is a namespace on the search path, checks whether the lock on the any namespace on the search path is set, and it it is, aborts the search and tries again; but otherwise returns either the key found (if `return-key?` is non-`nil`), or the value found otherwise.
+So what I think is, that we have a single top level function, `(::substrate:search-store key store return-key?)` (which we already sort of have in the 0.0.6 prototype, [here](https://www.journeyman.cc/post-scarcity/doc/html/intern_8c.html#a2189c0ab60e57a70adeb32aca99dbc43)). This searches a store (hashmap, namespace, association list, or hybrid association list) to find a binding for a key, and, having found that binding, then, if there is a namespace on the search path, checks whether the lock on the any namespace on the search path is set, and if it is, aborts the search and tries again; but otherwise returns either the key found (if `return-key?` is non-`nil`), or the value found otherwise.
 
 This function implements the user-level Lisp functions `assoc`, `interned`, and `interned?`. It also implements *hashmap-in-function-position* and *keyword-in-function-position*, in so far as both of these are treated as calls to `assoc`.
 
diff --git a/src/c/debug.h b/src/c/debug.h
index dc833dd..1f66a9f 100644
--- a/src/c/debug.h
+++ b/src/c/debug.h
@@ -17,6 +17,11 @@
 #include <stddef.h>
 #include <stdio.h>
 
+/*
+ * wide characters
+ */
+#include <wchar.h>
+#include <wctype.h>
 
 /**
  * @brief Print messages debugging memory allocation. 
diff --git a/src/c/memory/header.h b/src/c/memory/header.h
index 429cda1..42fa488 100644
--- a/src/c/memory/header.h
+++ b/src/c/memory/header.h
@@ -29,7 +29,7 @@ struct pso_header {
             char mnemonic[TAGLENGTH];
             /** size class for this object */
             uint8_t size_class;
-        } tag;
+        } bytes;
         /** the tag considered as a number */
         uint32_t value;
     } tag;
diff --git a/src/c/memory/memory.h b/src/c/memory/memory.h
index fc242c2..33e9d39 100644
--- a/src/c/memory/memory.h
+++ b/src/c/memory/memory.h
@@ -21,7 +21,7 @@
  * since managed objects require a two word header; it's unlikely that
  * these undersized size classes will be used at all.
  */
-#define MAX_SIZE_CLASS = 0xf
+#define MAX_SIZE_CLASS 0xf
 
 int initialise_memory(  );
 
diff --git a/src/c/memory/page.c b/src/c/memory/page.c
index 1486301..2fdaf79 100644
--- a/src/c/memory/page.c
+++ b/src/c/memory/page.c
@@ -9,7 +9,10 @@
 
 #include <math.h>
 #include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
 
+#include "debug.h"
 #include "memory/memory.h"
 #include "memory/node.h"
 #include "memory/page.h"
@@ -36,13 +39,13 @@
  * to hold the number of pages we *might* create at start up time. We need a
  * way to grow the number of pages, while keeping access to them cheap.
  */
-struct page * pages[NPAGES];
+union page * pages[NPAGES];
 
 /**
  * @brief the number of pages which have thus far been allocated.
  * 
  */
-uint32_t npages_allocated = 0
+uint32_t npages_allocated = 0;
 
 /**
  * @brief private to allocate_page; do not use.
@@ -51,10 +54,11 @@ uint32_t npages_allocated = 0
  * @param page_index its location in the pages[] array;
  * @param size_class the size class of objects in this page;
  * @param freelist the freelist for objects of this size class.
- * @return struct cons_pointer the new head for the freelist for this size_class,
+ * @return struct pso_pointer the new head for the freelist for this size_class,
  */
-struct cons_pointer initialise_page( struct page * page_addr, uint16_t page_index, uint8_t size_class, pso_pointer freelist) {
-    struct cons_pointer result = freelist;
+struct pso_pointer initialise_page( union page* page_addr, uint16_t page_index, 
+    uint8_t size_class, struct pso_pointer freelist) {
+    struct pso_pointer result = freelist;
     int obj_size = pow(2, size_class);
     int obj_bytes = obj_size  * sizeof(uint64_t);
     int objs_in_page = PAGE_BYTES/obj_bytes;
@@ -64,16 +68,14 @@ struct cons_pointer initialise_page( struct page * page_addr, uint16_t page_inde
     // `nil` and the next on for `t`.
     for (int i = objs_in_page - 1; i >= 0; i--) {
         // it should be safe to cast any pso object to a pso2
-        struct pso2* object = (pso2 *)(page_addr + (i * obj_bytes)); 
+        struct pso2* object = (struct pso2 *)(page_addr + (i * obj_bytes)); 
 
-        object->header.tag.size_class = size_class;
-        strncpy( (char *)(object->header.tag.mnemonic), FREETAG, TAGLENGTH);
+        object->header.tag.bytes.size_class = size_class;
+        strncpy( (char *)(object->header.tag.bytes.mnemonic), FREETAG, TAGLENGTH);
         object->payload.free.next = result;
 
         result = make_pointer( node_index, page_index, (uint16_t)( i * obj_size));
     }
-
-    return result;
 }
 
 /** 
@@ -89,8 +91,8 @@ struct cons_pointer initialise_page( struct page * page_addr, uint16_t page_inde
  * @param size_class an integer in the range 0...MAX_SIZE_CLASS.
  * @return t on success, an exception if an error occurred.
  */
-struct cons_pointer allocate_page( uint8_t size_class ) {
-    struct cons_pointer result = t;
+struct pso_pointer allocate_page( uint8_t size_class ) {
+    struct pso_pointer result = t;
 
     if ( npages_allocated == 0) {
         for (int i = 0; i < NPAGES; i++) {
@@ -101,17 +103,17 @@ struct cons_pointer allocate_page( uint8_t size_class ) {
 
     if ( npages_allocated < NPAGES) {    
         if ( size_class >= 2 && size_class <= MAX_SIZE_CLASS ) {
-            result = malloc( sizeof( page ) );
+            void* pg = malloc( sizeof( union page ) );
 
-            if ( result != NULL ) {
-                memset( result, 0, sizeof( page ) );
-                pages[ npages_allocated] = result;
+            if ( pg != NULL ) {
+                memset( pg, 0, sizeof( union page ) );
+                pages[ npages_allocated] = pg;
                 debug_printf( DEBUG_ALLOC, 0, 
                     L"Allocated page %d for objects of size class %x.\n", 
                     npages_allocated, size_class);
 
                 freelists[size_class] =
-                    initialise_page( result, npages_allocated, size_class, freelists[size_class] );
+                    initialise_page( (union page*)pg, npages_allocated, size_class, freelists[size_class] );
 
                 debug_printf( DEBUG_ALLOC, 0, 
                     L"Initialised page %d; freelist for size class %x updated.\n", 
diff --git a/src/c/memory/page.h b/src/c/memory/page.h
index 522b2fa..b5285f5 100644
--- a/src/c/memory/page.h
+++ b/src/c/memory/page.h
@@ -10,6 +10,7 @@
 #ifndef __psse_memory_page_h
 #define __psse_memory_page_h
 
+#include "memory/pointer.h"
 #include "memory/pso2.h"
 #include "memory/pso3.h"
 #include "memory/pso4.h"
@@ -38,7 +39,7 @@
  */
 #define NPAGES 64
 
-extern struct page *pages[NPAGES];
+extern union page *pages[NPAGES];
 
 /**
  * @brief A page is a megabyte of memory which contains objects all of which 
@@ -53,22 +54,25 @@ extern struct page *pages[NPAGES];
  * collection they will be returned to that freelist. 
  */
 union page {
-    uint8_t[PAGE_BYTES] bytes;
-    uint64_t[PAGE_BYTES / 8] words;
-    struct pso2[PAGE_BYTES / 32] pso2s;
-    struct pso3[PAGE_BYTES / 64] pso3s;
-    struct pso4[PAGE_BYTES / 128] pso4s;
-    struct pso5[PAGE_BYTES / 256] pso5s;
-    struct pso6[PAGE_BYTES / 512] pso6s;
-    struct pso7[PAGE_BYTES / 1024] pso7s;
-    struct pso8[PAGE_BYTES / 2048] pso8s;
-    struct pso9[PAGE_BYTES / 4096] pso9s;
-    struct psoa[PAGE_BYTES / 8192] psoas;
-    struct psob[PAGE_BYTES / 16384] psobs;
-    struct psoc[PAGE_BYTES / 32768] psocs;
-    struct psod[PAGE_BYTES / 65536] psods;
-    struct psoe[PAGE_BYTES / 131072] psoes;
-    struct psof[PAGE_BYTES / 262144] psofs;
+    uint8_t bytes[PAGE_BYTES];
+    uint64_t words[PAGE_BYTES / 8];
+    struct pso2 pso2s[PAGE_BYTES / 32];
+    struct pso3 pso3s[PAGE_BYTES / 64];
+    struct pso4 pso4s[PAGE_BYTES / 128];
+    struct pso5 pso5s[PAGE_BYTES / 256];
+    struct pso6 pso6s[PAGE_BYTES / 512];
+    struct pso7 pso7s[PAGE_BYTES / 1024];
+    struct pso8 pso8s[PAGE_BYTES / 2048];
+    struct pso9 pso9s[PAGE_BYTES / 4096];
+    struct psoa psoas[PAGE_BYTES / 8192];
+    struct psob psobs[PAGE_BYTES / 16384];
+    struct psoc psocs[PAGE_BYTES / 32768];
+    struct psod psods[PAGE_BYTES / 65536];
+    struct psoe psoes[PAGE_BYTES / 131072];
+    struct psof psofs[PAGE_BYTES / 262144];
 };
 
+struct pso_pointer initialise_page( union page * page_addr, uint16_t page_index, 
+    uint8_t size_class, struct pso_pointer freelist);
+
 #endif
diff --git a/src/c/memory/pso.h b/src/c/memory/pso.h
index 9fd7cc1..5f91bca 100644
--- a/src/c/memory/pso.h
+++ b/src/c/memory/pso.h
@@ -14,234 +14,234 @@
 
 #include "memory/header.h"
 #include "memory/pointer.h"
-#include "payloads/cons.h"
-#include "payloads/exception.h"
-#include "payloads/free.h"
-#include "payloads/function.h"
-#include "payloads/hashtable.h"
-#include "payloads/integer.h"
-#include "payloads/keyword.h"
-#include "payloads/lambda.h"
-#include "payloads/mutex.h"
-#include "payloads/namespace.h"
-#include "payloads/nlambda.h"
-#include "payloads/read_stream.h"
-#include "payloads/special.h"
-#include "payloads/stack.h"
-#include "payloads/string.h"
-#include "payloads/symbol.h"
-#include "payloads/time.h"
-#include "payloads/vector_pointer.h"
-#include "payloads/write_stream.h"
+// #include "payloads/cons.h"
+// #include "payloads/exception.h"
+// #include "payloads/free.h"
+// #include "payloads/function.h"
+// #include "payloads/hashtable.h"
+// #include "payloads/integer.h"
+// #include "payloads/keyword.h"
+// #include "payloads/lambda.h"
+// #include "payloads/mutex.h"
+// #include "payloads/namespace.h"
+// #include "payloads/nlambda.h"
+// #include "payloads/read_stream.h"
+// #include "payloads/special.h"
+// #include "payloads/stack.h"
+// #include "payloads/string.h"
+// #include "payloads/symbol.h"
+// #include "payloads/time.h"
+// #include "payloads/vector_pointer.h"
+// #include "payloads/write_stream.h"
 
-/**
- * @brief A paged space object of size class 2, four words total, two words
- * payload.
- * 
- */
-struct pso2 {
-    struct pso_header header;
-    union {
-        char bytes[16];
-        uint64_t words[2];
-        struct cons_payload cons;
-        struct free_payload free;
-        struct function_payload function;
-        struct integer_payload integer;
-        struct lambda_payload lambda;
-        struct special_payload special;
-        struct stream_payload stream;
-        struct time_payload time;
-        struct vectorp_payload vectorp;
-    } payload;
-};
+// /**
+//  * @brief A paged space object of size class 2, four words total, two words
+//  * payload.
+//  * 
+//  */
+// struct pso2 {
+//     struct pso_header header;
+//     union {
+//         char bytes[16];
+//         uint64_t words[2];
+//         struct cons_payload cons;
+//         struct free_payload free;
+//         struct function_payload function;
+//         struct integer_payload integer;
+//         struct lambda_payload lambda;
+//         struct special_payload special;
+//         struct stream_payload stream;
+//         struct time_payload time;
+//         struct vectorp_payload vectorp;
+//     } payload;
+// };
 
-/**
- * @brief A paged space object of size class 3, 8 words total, 6 words
- * payload.
- * 
- */
-struct pso3 {
-    struct pso_header header;
-    union {
-        char bytes[48];
-        uint64_t words[6];
-        struct exception_payload exception;
-        struct free_payload free;
-        struct mutex_payload mutex;
-    } payload;
-};
+// /**
+//  * @brief A paged space object of size class 3, 8 words total, 6 words
+//  * payload.
+//  * 
+//  */
+// struct pso3 {
+//     struct pso_header header;
+//     union {
+//         char bytes[48];
+//         uint64_t words[6];
+//         struct exception_payload exception;
+//         struct free_payload free;
+//         struct mutex_payload mutex;
+//     } payload;
+// };
 
-/**
- * @brief A paged space object of size class 4, 16 words total, 14 words
- * payload.
- * 
- */
-struct pso4 {
-    struct pso_header header;
-    union {
-        char bytes[112];
-        uint64_t words[14];
-        struct free_payload free;
-        struct stack_frame_payload stack_frame;
-    } payload;
-};
+// /**
+//  * @brief A paged space object of size class 4, 16 words total, 14 words
+//  * payload.
+//  * 
+//  */
+// struct pso4 {
+//     struct pso_header header;
+//     union {
+//         char bytes[112];
+//         uint64_t words[14];
+//         struct free_payload free;
+//         struct stack_frame_payload stack_frame;
+//     } payload;
+// };
 
-/**
- * @brief A paged space object of size class 5, 32 words total, 30 words
- * payload.
- * 
- */
-struct pso5 {
-    struct pso_header header;
-    union {
-        char bytes[240];
-        uint64_t words[30];
-        struct free_payload free;
-    } payload;
-};
+// /**
+//  * @brief A paged space object of size class 5, 32 words total, 30 words
+//  * payload.
+//  * 
+//  */
+// struct pso5 {
+//     struct pso_header header;
+//     union {
+//         char bytes[240];
+//         uint64_t words[30];
+//         struct free_payload free;
+//     } payload;
+// };
 
-/**
- * @brief A paged space object of size class 6, 64 words total, 62 words
- * payload.
- * 
- */
-struct pso6 {
-    struct pso_header header;
-    union {
-        char bytes[496];
-        uint64_t words[62];
-        struct free_payload free;
-        struct hashtable_payload hashtable;
-        struct namespace_payload namespace;
-    } payload;
-};
+// /**
+//  * @brief A paged space object of size class 6, 64 words total, 62 words
+//  * payload.
+//  * 
+//  */
+// struct pso6 {
+//     struct pso_header header;
+//     union {
+//         char bytes[496];
+//         uint64_t words[62];
+//         struct free_payload free;
+//         struct hashtable_payload hashtable;
+//         struct namespace_payload namespace;
+//     } payload;
+// };
 
-/**
- * @brief A paged space object of size class 7, 128 words total, 126 words
- * payload.
- * 
- */
-struct pso7 {
-    struct pso_header header;
-    union {
-        char bytes[1008];
-        uint64_t words[126];
-        struct free_payload free;
-    } payload;
-};
+// /**
+//  * @brief A paged space object of size class 7, 128 words total, 126 words
+//  * payload.
+//  * 
+//  */
+// struct pso7 {
+//     struct pso_header header;
+//     union {
+//         char bytes[1008];
+//         uint64_t words[126];
+//         struct free_payload free;
+//     } payload;
+// };
 
-/**
- * @brief A paged space object of size class 8, 256 words total, 254 words
- * payload.
- * 
- */
-struct pso8 {
-    struct pso_header header;
-    union {
-        char bytes[2032];
-        uint64_t words[254];
-        struct free_payload free;
-    } payload;
-};
+// /**
+//  * @brief A paged space object of size class 8, 256 words total, 254 words
+//  * payload.
+//  * 
+//  */
+// struct pso8 {
+//     struct pso_header header;
+//     union {
+//         char bytes[2032];
+//         uint64_t words[254];
+//         struct free_payload free;
+//     } payload;
+// };
 
-/**
- * @brief A paged space object of size class 9, 512 words total, 510 words
- * payload.
- * 
- */
-struct pso9 {
-    struct pso_header header;
-    union {
-        char bytes[4080];
-        uint64_t words[510];
-        struct free_payload free;
-    } payload;
-};
+// /**
+//  * @brief A paged space object of size class 9, 512 words total, 510 words
+//  * payload.
+//  * 
+//  */
+// struct pso9 {
+//     struct pso_header header;
+//     union {
+//         char bytes[4080];
+//         uint64_t words[510];
+//         struct free_payload free;
+//     } payload;
+// };
 
-/**
- * @brief A paged space object of size class a, 1024 words total, 1022 words
- * payload.
- * 
- */
-struct psoa {
-    struct pso_header header;
-    union {
-        char bytes[8176];
-        uint64_t words[1022];
-        struct free_payload free;
-    } payload;
-};
+// /**
+//  * @brief A paged space object of size class a, 1024 words total, 1022 words
+//  * payload.
+//  * 
+//  */
+// struct psoa {
+//     struct pso_header header;
+//     union {
+//         char bytes[8176];
+//         uint64_t words[1022];
+//         struct free_payload free;
+//     } payload;
+// };
 
-/**
- * @brief A paged space object of size class b, 2048 words total, 2046 words
- * payload.
- * 
- */
-struct psob {
-    struct pso_header header;
-    union {
-        char bytes[16368];
-        uint64_t words[2046];
-        struct free_payload free;
-    } payload;
-};
+// /**
+//  * @brief A paged space object of size class b, 2048 words total, 2046 words
+//  * payload.
+//  * 
+//  */
+// struct psob {
+//     struct pso_header header;
+//     union {
+//         char bytes[16368];
+//         uint64_t words[2046];
+//         struct free_payload free;
+//     } payload;
+// };
 
-/**
- * @brief A paged space object of size class c, 4096 words total, 4094 words
- * payload.
- * 
- */
-struct psoc {
-    struct pso_header header;
-    union {
-        char bytes[32752];
-        uint64_t words[4094];
-        struct free_payload free;
-    } payload;
-};
+// /**
+//  * @brief A paged space object of size class c, 4096 words total, 4094 words
+//  * payload.
+//  * 
+//  */
+// struct psoc {
+//     struct pso_header header;
+//     union {
+//         char bytes[32752];
+//         uint64_t words[4094];
+//         struct free_payload free;
+//     } payload;
+// };
 
-/**
- * @brief A paged space object of size class d, 8192 words total, 8190 words
- * payload.
- * 
- */
-struct psod {
-    struct pso_header header;
-    union {
-        char bytes[65520];
-        uint64_t words[8190];
-        struct free_payload free;
-    } payload;
-};
+// /**
+//  * @brief A paged space object of size class d, 8192 words total, 8190 words
+//  * payload.
+//  * 
+//  */
+// struct psod {
+//     struct pso_header header;
+//     union {
+//         char bytes[65520];
+//         uint64_t words[8190];
+//         struct free_payload free;
+//     } payload;
+// };
 
-/**
- * @brief A paged space object of size class e, 16384 words total, 16382 words
- * payload.
- * 
- */
-struct psoe {
-    struct pso_header header;
-    union {
-        char bytes[131056];
-        uint64_t words[16382];
-        struct free_payload free;
-    } payload;
-};
+// /**
+//  * @brief A paged space object of size class e, 16384 words total, 16382 words
+//  * payload.
+//  * 
+//  */
+// struct psoe {
+//     struct pso_header header;
+//     union {
+//         char bytes[131056];
+//         uint64_t words[16382];
+//         struct free_payload free;
+//     } payload;
+// };
 
-/**
- * @brief A paged space object of size class f, 32768 words total, 32766 words
- * payload.
- * 
- */
-struct psof {
-    struct pso_header header;
-    union {
-        char bytes[262128];
-        uint64_t words[32766];
-        struct free_payload free;
-    } payload;
-};
+// /**
+//  * @brief A paged space object of size class f, 32768 words total, 32766 words
+//  * payload.
+//  * 
+//  */
+// struct psof {
+//     struct pso_header header;
+//     union {
+//         char bytes[262128];
+//         uint64_t words[32766];
+//         struct free_payload free;
+//     } payload;
+// };
 
 struct pso_pointer allocate( char* tag, uint8_t size_class);
 
diff --git a/src/c/memory/pso2.h b/src/c/memory/pso2.h
new file mode 100644
index 0000000..e8305d0
--- /dev/null
+++ b/src/c/memory/pso2.h
@@ -0,0 +1,53 @@
+/**
+ *  memory/pso2.h
+ *
+ *  Paged space object of size class 2, four words total, two words payload.
+ *
+ *  (c) 2026 Simon Brooke <simon@journeyman.cc>
+ *  Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#ifndef __psse_memory_pso2_h
+#define __psse_memory_pso2_h
+
+#include <stdint.h>
+
+#include "memory/header.h"
+#include "payloads/cons.h"
+#include "payloads/free.h"
+#include "payloads/function.h"
+#include "payloads/integer.h"
+#include "payloads/keyword.h"
+#include "payloads/lambda.h"
+#include "payloads/nlambda.h"
+#include "payloads/read_stream.h"
+#include "payloads/special.h"
+#include "payloads/string.h"
+#include "payloads/symbol.h"
+// #include "payloads/time.h"
+#include "payloads/vector_pointer.h"
+#include "payloads/write_stream.h"
+
+/**
+ * @brief A paged space object of size class 2, four words total, two words
+ * payload.
+ * 
+ */
+struct pso2 {
+    struct pso_header header;
+    union {
+        char bytes[16];
+        uint64_t words[2];
+        struct cons_payload cons;
+        struct free_payload free;
+        struct function_payload function;
+        struct integer_payload integer;
+        struct lambda_payload lambda;
+//        struct special_payload special;
+        struct stream_payload stream;
+//        struct time_payload time;
+        struct vectorp_payload vectorp;
+    } payload;
+};
+
+#endif
diff --git a/src/c/memory/pso3.h b/src/c/memory/pso3.h
new file mode 100644
index 0000000..c4975b1
--- /dev/null
+++ b/src/c/memory/pso3.h
@@ -0,0 +1,37 @@
+/**
+ *  memory/pso3.h
+ *
+ *  Paged space object of size class 3, 8 words total, 6 words payload.
+ *
+ *  (c) 2026 Simon Brooke <simon@journeyman.cc>
+ *  Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#ifndef __psse_memory_pso3_h
+#define __psse_memory_pso3_h
+
+#include <stdint.h>
+
+#include "memory/header.h"
+#include "payloads/exception.h"
+#include "payloads/free.h"
+#include "payloads/mutex.h"
+
+
+/**
+ * @brief A paged space object of size class 3, 8 words total, 6 words
+ * payload.
+ * 
+ */
+struct pso3 {
+    struct pso_header header;
+    union {
+        char bytes[48];
+        uint64_t words[6];
+        struct exception_payload exception;
+        struct free_payload free;
+        struct mutex_payload mutex;
+    } payload;
+};
+
+#endif
diff --git a/src/c/memory/pso4.h b/src/c/memory/pso4.h
new file mode 100644
index 0000000..9ffc337
--- /dev/null
+++ b/src/c/memory/pso4.h
@@ -0,0 +1,34 @@
+/**
+ *  memory/pso4.h
+ *
+ *  Paged space object of size class 4, 16 words total, 14 words payload.
+ *
+ *  (c) 2026 Simon Brooke <simon@journeyman.cc>
+ *  Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#ifndef __psse_memory_pso4_h
+#define __psse_memory_pso4_h
+
+#include <stdint.h>
+
+#include "memory/header.h"
+#include "payloads/free.h"
+#include "payloads/stack.h"
+
+/**
+ * @brief A paged space object of size class 4, 16 words total, 14 words
+ * payload.
+ * 
+ */
+struct pso4 {
+    struct pso_header header;
+    union {
+        char bytes[112];
+        uint64_t words[14];
+        struct free_payload free;
+        struct stack_frame_payload stack_frame;
+    } payload;
+};
+
+#endif
diff --git a/src/c/memory/pso5.h b/src/c/memory/pso5.h
new file mode 100644
index 0000000..585332c
--- /dev/null
+++ b/src/c/memory/pso5.h
@@ -0,0 +1,32 @@
+/**
+ *  memory/pso5.h
+ *
+ *  Paged space object of size class 5, 32 words total, 30 words payload.
+ *
+ *  (c) 2026 Simon Brooke <simon@journeyman.cc>
+ *  Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#ifndef __psse_memory_pso5_h
+#define __psse_memory_pso5_h
+
+#include <stdint.h>
+
+#include "memory/header.h"
+#include "payloads/free.h"
+
+/**
+ * @brief A paged space object of size class 5, 32 words total, 30 words
+ * payload.
+ * 
+ */
+struct pso5 {
+    struct pso_header header;
+    union {
+        char bytes[240];
+        uint64_t words[30];
+        struct free_payload free;
+    } payload;
+};
+
+#endif
diff --git a/src/c/memory/pso6.h b/src/c/memory/pso6.h
new file mode 100644
index 0000000..3bd9290
--- /dev/null
+++ b/src/c/memory/pso6.h
@@ -0,0 +1,32 @@
+/**
+ *  memory/pso6.h
+ *
+ *  Paged space object of size class 6, 64 words total, 62 words payload.
+ *
+ *  (c) 2026 Simon Brooke <simon@journeyman.cc>
+ *  Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#ifndef __psse_memory_pso6_h
+#define __psse_memory_pso6_h
+
+#include <stdint.h>
+
+#include "memory/header.h"
+#include "payloads/free.h"
+
+/**
+ * @brief A paged space object of size class 6, 64 words total, 62 words
+ * payload.
+ * 
+ */
+struct pso6 {
+    struct pso_header header;
+    union {
+        char bytes[496];
+        uint64_t words[62];
+        struct free_payload free;
+    } payload;
+};
+
+#endif
diff --git a/src/c/memory/pso7.h b/src/c/memory/pso7.h
new file mode 100644
index 0000000..04ee61b
--- /dev/null
+++ b/src/c/memory/pso7.h
@@ -0,0 +1,32 @@
+/**
+ *  memory/pso7.h
+ *
+ *  Paged space object of size class 7, 128 words total, 126 words payload.
+ *
+ *  (c) 2026 Simon Brooke <simon@journeyman.cc>
+ *  Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#ifndef __psse_memory_pso7_h
+#define __psse_memory_pso7_h
+
+#include <stdint.h>
+
+#include "memory/header.h"
+#include "payloads/free.h"
+
+/**
+ * @brief A paged space object of size class 7, 128 words total, 126 words
+ * payload.
+ * 
+ */
+struct pso7 {
+    struct pso_header header;
+    union {
+        char bytes[1008];
+        uint64_t words[126];
+        struct free_payload free;
+    } payload;
+};
+
+#endif
diff --git a/src/c/memory/pso8.h b/src/c/memory/pso8.h
new file mode 100644
index 0000000..b3a00bc
--- /dev/null
+++ b/src/c/memory/pso8.h
@@ -0,0 +1,32 @@
+/**
+ *  memory/pso8.h
+ *
+ *  Paged space object of size class 8, 256 words total, 254 words payload.
+ *
+ *  (c) 2026 Simon Brooke <simon@journeyman.cc>
+ *  Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#ifndef __psse_memory_pso8_h
+#define __psse_memory_pso8_h
+
+#include <stdint.h>
+
+#include "memory/header.h"
+#include "payloads/free.h"
+
+/**
+ * @brief A paged space object of size class 8, 256 words total, 254 words
+ * payload.
+ * 
+ */
+struct pso8 {
+    struct pso_header header;
+    union {
+        char bytes[2032];
+        uint64_t words[254];
+        struct free_payload free;
+    } payload;
+};
+
+#endif
diff --git a/src/c/memory/pso9.h b/src/c/memory/pso9.h
new file mode 100644
index 0000000..3fa5eab
--- /dev/null
+++ b/src/c/memory/pso9.h
@@ -0,0 +1,32 @@
+/**
+ *  memory/pso9.h
+ *
+ *  Paged space object of size class 9, 512 words total, 510 words payload.
+ *
+ *  (c) 2026 Simon Brooke <simon@journeyman.cc>
+ *  Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#ifndef __psse_memory_pso9_h
+#define __psse_memory_pso9_h
+
+#include <stdint.h>
+
+#include "memory/header.h"
+#include "payloads/free.h"
+
+/**
+ * @brief A paged space object of size class 9, 512 words total, 510 words
+ * payload.
+ * 
+ */
+struct pso9 {
+    struct pso_header header;
+    union {
+        char bytes[4080];
+        uint64_t words[510];
+        struct free_payload free;
+    } payload;
+};
+
+#endif
diff --git a/src/c/memory/psoa.h b/src/c/memory/psoa.h
new file mode 100644
index 0000000..1c8e9c7
--- /dev/null
+++ b/src/c/memory/psoa.h
@@ -0,0 +1,32 @@
+/**
+ *  memory/psoa.h
+ *
+ *  Paged space object of size class a, 1024 words total, 1022 words payload.
+ *
+ *  (c) 2026 Simon Brooke <simon@journeyman.cc>
+ *  Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#ifndef __psse_memory_psoa_h
+#define __psse_memory_psoa_h
+
+#include <stdint.h>
+
+#include "memory/header.h"
+#include "payloads/free.h"
+
+/**
+ * @brief A paged space object of size class a, 1024 words total, 1022 words
+ * payload.
+ * 
+ */
+struct psoa {
+    struct pso_header header;
+    union {
+        char bytes[8176];
+        uint64_t words[1022];
+        struct free_payload free;
+    } payload;
+};
+
+#endif
diff --git a/src/c/memory/psob.h b/src/c/memory/psob.h
new file mode 100644
index 0000000..d6b235a
--- /dev/null
+++ b/src/c/memory/psob.h
@@ -0,0 +1,32 @@
+/**
+ *  memory/psob.h
+ *
+ *  Paged space object of size class b, 2048 words total, 2046 words payload.
+ *
+ *  (c) 2026 Simon Brooke <simon@journeyman.cc>
+ *  Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#ifndef __psse_memory_psob_h
+#define __psse_memory_psob_h
+
+#include <stdint.h>
+
+#include "memory/header.h"
+#include "payloads/free.h"
+
+/**
+ * @brief A paged space object of size class b, 2048 words total, 2046 words
+ * payload.
+ * 
+ */
+struct psob {
+    struct pso_header header;
+    union {
+        char bytes[16368];
+        uint64_t words[2046];
+        struct free_payload free;
+    } payload;
+};
+
+#endif
diff --git a/src/c/memory/psoc.h b/src/c/memory/psoc.h
new file mode 100644
index 0000000..934c8b3
--- /dev/null
+++ b/src/c/memory/psoc.h
@@ -0,0 +1,32 @@
+/**
+ *  memory/psoc.h
+ *
+ *  Paged space object of size class c, 4096 words total, 4094 words payload.
+ *
+ *  (c) 2026 Simon Brooke <simon@journeyman.cc>
+ *  Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#ifndef __psse_memory_psoc_h
+#define __psse_memory_psoc_h
+
+#include <stdint.h>
+
+#include "memory/header.h"
+#include "payloads/free.h"
+
+/**
+ * @brief A paged space object of size class c, 4096 words total, 4094 words
+ * payload.
+ * 
+ */
+struct psoc {
+    struct pso_header header;
+    union {
+        char bytes[32752];
+        uint64_t words[4094];
+        struct free_payload free;
+    } payload;
+};
+
+#endif
diff --git a/src/c/memory/psod.h b/src/c/memory/psod.h
new file mode 100644
index 0000000..5ed7711
--- /dev/null
+++ b/src/c/memory/psod.h
@@ -0,0 +1,32 @@
+/**
+ *  memory/psod.h
+ *
+ *  Paged space object of size class d, 8192 words total, 8190 words payload.
+ *
+ *  (c) 2026 Simon Brooke <simon@journeyman.cc>
+ *  Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#ifndef __psse_memory_psod_h
+#define __psse_memory_psod_h
+
+#include <stdint.h>
+
+#include "memory/header.h"
+#include "payloads/free.h"
+
+/**
+ * @brief A paged space object of size class d, 8192 words total, 8190 words
+ * payload.
+ * 
+ */
+struct psod {
+    struct pso_header header;
+    union {
+        char bytes[65520];
+        uint64_t words[8190];
+        struct free_payload free;
+    } payload;
+};
+
+#endif
diff --git a/src/c/memory/psoe.h b/src/c/memory/psoe.h
new file mode 100644
index 0000000..5f2b619
--- /dev/null
+++ b/src/c/memory/psoe.h
@@ -0,0 +1,32 @@
+/**
+ *  memory/psoe.h
+ *
+ *  Paged space object of size class e, 16384 words total, 16382 words payload.
+ *
+ *  (c) 2026 Simon Brooke <simon@journeyman.cc>
+ *  Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#ifndef __psse_memory_psoe_h
+#define __psse_memory_psoe_h
+
+#include <stdint.h>
+
+#include "memory/header.h"
+#include "payloads/free.h"
+
+/**
+ * @brief A paged space object of size class e, 16384 words total, 16382 words
+ * payload.
+ * 
+ */
+struct psoe {
+    struct pso_header header;
+    union {
+        char bytes[131056];
+        uint64_t words[16382];
+        struct free_payload free;
+    } payload;
+};
+
+#endif
diff --git a/src/c/memory/psof.h b/src/c/memory/psof.h
new file mode 100644
index 0000000..58615de
--- /dev/null
+++ b/src/c/memory/psof.h
@@ -0,0 +1,32 @@
+/**
+ *  memory/psof.h
+ *
+ *  Paged space object of size class f, 32768 words total, 32766 words payload.
+ *
+ *  (c) 2026 Simon Brooke <simon@journeyman.cc>
+ *  Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#ifndef __psse_memory_psof_h
+#define __psse_memory_psof_h
+
+#include <stdint.h>
+
+#include "memory/header.h"
+#include "payloads/free.h"
+
+/**
+ * @brief A paged space object of size class f, 32768 words total, 32766 words
+ * payload.
+ * 
+ */
+struct psof {
+    struct pso_header header;
+    union {
+        char bytes[262128];
+        uint64_t words[32766];
+        struct free_payload free;
+    } payload;
+};
+
+#endif
diff --git a/src/c/payloads/cons.c b/src/c/payloads/cons.c
index 5eaf2b6..6a002c8 100644
--- a/src/c/payloads/cons.c
+++ b/src/c/payloads/cons.c
@@ -12,6 +12,7 @@
 #include "memory/node.h"
 #include "memory/pointer.h"
 #include "memory/pso.h"
+#include "memory/pso2.h"
 #include "payloads/cons.h"
 
 /**
diff --git a/src/c/payloads/function.h b/src/c/payloads/function.h
index 2ef45c4..2f43bef 100644
--- a/src/c/payloads/function.h
+++ b/src/c/payloads/function.h
@@ -11,7 +11,7 @@
 #define __psse_payloads_function_h
 
 #include "memory/pointer.h"
-#include "memory/pso.h"
+#include "memory/pso4.h"
 
 /**
  * @brief Tag for an ordinary Lisp function - one whose arguments are pre-evaluated.
@@ -41,7 +41,7 @@ struct function_payload {
      * a cons pointer (representing its result).
      * \todo check this documentation is current!
      */
-    struct pso_pointer ( *executable ) ( struct pso4 *,
+    struct pso_pointer ( *executable ) ( struct pso4*,
                                           struct pso_pointer,
                                           struct pso_pointer );
 };
diff --git a/src/c/payloads/hashtable.h b/src/c/payloads/hashtable.h
index 86664e5..3619847 100644
--- a/src/c/payloads/hashtable.h
+++ b/src/c/payloads/hashtable.h
@@ -45,11 +45,11 @@
  * i.e. either an assoc list or a further hashtable.
  */
 struct hashtable_payload {
-    struct cons_pointer hash_fn;    /* function for hashing values in this hashtable, or `NIL` to use
+    struct pso_pointer hash_fn;    /* function for hashing values in this hashtable, or `NIL` to use
                                      the default hashing function */
     uint32_t n_buckets;             /* number of hash buckets */
-    struct cons_pointer buckets[];  /* actual hash buckets, which should be `NIL`
+    struct pso_pointer buckets[];  /* actual hash buckets, which should be `NIL`
                                      * or assoc lists or (possibly) further hashtables. */
 };
 
-#endif
\ No newline at end of file
+#endif
diff --git a/src/c/payloads/namespace.h b/src/c/payloads/namespace.h
index b494e93..bb1b1b3 100644
--- a/src/c/payloads/namespace.h
+++ b/src/c/payloads/namespace.h
@@ -48,17 +48,17 @@
  * i.e. either an assoc list or a further namespace.
  */
 struct namespace_payload {
-    struct cons_pointer hash_fn;    /* function for hashing values in this namespace, or 
+    struct pso_pointer hash_fn;    /* function for hashing values in this namespace, or 
                                      * `NIL` to use the default hashing function */
     uint32_t n_buckets;             /* number of hash buckets */
     uint32_t unused;                /* for word alignment and possible later expansion */
-    struct cons_pointer write_acl;  /* it seems to me that it is likely that the
+    struct pso_pointer write_acl;  /* it seems to me that it is likely that the
                                      * principal difference between a hashtable and a
                                      * namespace is that a hashtable has a write ACL
                                      * of `NIL`, meaning not writeable by anyone */
-    struct cons_pointer mutex;      /* the mutex to lock when modifying this namespace.*/
-    struct cons_pointer buckets[];  /* actual hash buckets, which should be `NIL`
+    struct pso_pointer mutex;      /* the mutex to lock when modifying this namespace.*/
+    struct pso_pointer buckets[];  /* actual hash buckets, which should be `NIL`
                                      * or assoc lists or (possibly) further hashtables. */
 };
 
-#endif
\ No newline at end of file
+#endif
diff --git a/src/c/payloads/read_stream.h b/src/c/payloads/read_stream.h
index e271489..ef2f5cc 100644
--- a/src/c/payloads/read_stream.h
+++ b/src/c/payloads/read_stream.h
@@ -14,6 +14,7 @@
 
 #include <curl/curl.h>
 
+#include "io/fopen.h"
 #include "memory/pointer.h"
 
 /**
@@ -31,7 +32,7 @@ struct stream_payload {
     /** metadata on the stream (e.g. its file attributes if a file, its HTTP
      * headers if a URL, etc). Expected to be an association, or nil. Not yet
      * implemented. */
-    struct cons_pointer meta;
+    struct pso_pointer meta;
 };
 
 #endif
diff --git a/src/c/payloads/special.h b/src/c/payloads/special.h
index 4c64545..4dcf7c2 100644
--- a/src/c/payloads/special.h
+++ b/src/c/payloads/special.h
@@ -11,6 +11,7 @@
 #define __psse_payloads_special_h
 
 #include "memory/pointer.h"
+#include "memory/pso4.h"
 
 /**
  * A special form - one whose arguments are not pre-evaluated but passed as
@@ -20,25 +21,25 @@
 #define SPECIALTAG  "SFM"
 #define SPECIALTV   5064275
 
-/**
- * @brief Payload of a special form cell. 
- *
- * Currently identical to the payload of a function cell.
- * \see function_payload
- */
-struct special_payload {
-    /**
-     * pointer to the source from which the special form was compiled, or NIL
-     * if it is a primitive.
-     */
-    struct pso_pointer meta;
-    /**  pointer to a function which takes a cons pointer (representing
-     * its argument list) and a cons pointer (representing its environment) and a
-     * stack frame (representing the previous stack frame) as arguments and returns
-     * a cons pointer (representing its result). */
-    struct pso_pointer ( *executable ) ( struct pso4 *,
-                                          struct pso_pointer,
-                                          struct pso_pointer );
-};
+// /**
+//  * @brief Payload of a special form cell. 
+//  *
+//  * Currently identical to the payload of a function cell.
+//  * \see function_payload
+//  */
+// struct special_payload {
+//     /**
+//      * pointer to the source from which the special form was compiled, or NIL
+//      * if it is a primitive.
+//      */
+//     struct pso_pointer meta;
+//     /**  pointer to a function which takes a cons pointer (representing
+//      * its argument list) and a cons pointer (representing its environment) and a
+//      * stack frame (representing the previous stack frame) as arguments and returns
+//      * a cons pointer (representing its result). */
+//     struct pso_pointer ( *executable ) ( struct pso4*,
+//                                           struct pso_pointer,
+//                                           struct pso_pointer );
+// };
 
 #endif
diff --git a/src/c/payloads/stack.c b/src/c/payloads/stack.c
index a814699..5cb2113 100644
--- a/src/c/payloads/stack.c
+++ b/src/c/payloads/stack.c
@@ -8,7 +8,8 @@
  */
 
 #include "memory/node.h"
-#include "memory/pso.h"
+#include "memory/pso2.h"
+#include "memory/pso4.h"
 #include "payloads/stack.h"
 
 /** 
diff --git a/src/c/payloads/stack.h b/src/c/payloads/stack.h
index ba0abd8..4225dbc 100644
--- a/src/c/payloads/stack.h
+++ b/src/c/payloads/stack.h
@@ -14,6 +14,9 @@
 
 #include "memory/pointer.h"
 
+#define STACKTAG "STK"
+#define STACKTV  4936787
+
 /*
  * number of arguments stored in a stack frame
  */
diff --git a/src/c/payloads/time.h b/src/c/payloads/time.h
index d9870b4..cc1ef0a 100644
--- a/src/c/payloads/time.h
+++ b/src/c/payloads/time.h
@@ -10,6 +10,8 @@
 #ifndef __psse_payloads_cons_h
 #define __psse_payloads_cons_h
 
+#include <stdint.h>
+
 #include "memory/pointer.h"
 
 /**
@@ -24,7 +26,7 @@
  * convenience, 14Bn years before 1st Jan 1970 (the UNIX epoch))
  */
 struct time_payload {
-    unsigned __int128 value;
+    unsigned __int128_t value;
 };
 
 #endif
diff --git a/src/c/payloads/vector_pointer.h b/src/c/payloads/vector_pointer.h
index b5e5f1c..8fda0f3 100644
--- a/src/c/payloads/vector_pointer.h
+++ b/src/c/payloads/vector_pointer.h
@@ -16,6 +16,7 @@
  * A pointer to an object in vector space.
  */
 #define VECTORPOINTTAG  "VSP"
+#define VECTORPOINTTV   5264214
 
 /**
  * @brief payload of a vector pointer cell.
diff --git a/src/c/payloads/write_stream.h b/src/c/payloads/write_stream.h
index deda598..1197d73 100644
--- a/src/c/payloads/write_stream.h
+++ b/src/c/payloads/write_stream.h
@@ -10,6 +10,7 @@
 #ifndef __psse_payloads_write_stream_h
 #define __psse_payloads_write_stream_h
 
+#include "io/fopen.h"
 #include "memory/pointer.h"
 
 /**
diff --git a/src/c/psse.c b/src/c/psse.c
index 5c67b6f..5f5f2fb 100644
--- a/src/c/psse.c
+++ b/src/c/psse.c
@@ -99,7 +99,7 @@ int main( int argc, char *argv[] ) {
 
     initialise_node( 0 );
 
-    repl(  );
+    // repl(  );
 
     exit( 0 );
 }
diff --git a/src/c/psse.h b/src/c/psse.h
index 0c57020..0fe9b43 100644
--- a/src/c/psse.h
+++ b/src/c/psse.h
@@ -24,7 +24,7 @@
 
 #include "debug.h"
 #include "memory/memory.h"
-#include "memory/stack.h"
+#include "payloads/stack.h"
 #include "version.h"
 
 #endif