Initial commit

.gitignore

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+sectcl.bin

Makefile

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+sectcl.bin: sectcl.nasm
+	nasm sectcl.nasm -f bin -o sectcl.bin
+
+hexdump: sectcl.bin
+	hexdump -C sectcl.bin
+
+qemu: sectcl.bin
+	qemu-system-i386 -fda sectcl.bin
+
+gdb: sectcl.bin
+	gdb -ex "target remote | qemu-system-i386 -S -gdb stdio -fda sectcl.bin -m 16" -ex "break *0x7c00" -ex "continue"
+
+objdump: sectcl.bin
+	objdump -D -Mintel,i8086 -b binary -m i386 sectcl.bin
+
+quecl: quecl.c
+	gcc -Os -o quecl quecl.c -Wall -Wextra
+
+clean:
+	rm sectcl.bin

README.md

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+# An attempt at a single-sector x86-16 Tcl interpreter
+Inspired by sectorFORTH, sectorLISP and Picol.

quecl.c

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+// Quecl - a quecto-sized Tcl-inspired programming language
+
+#include <stddef.h>
+#include <stdio.h>
+#define MEM_SIZE 32 * 1024  // 32 kilobytes
+char MEMORY[MEM_SIZE];
+size_t basepointer = 0;
+size_t stack = 0;
+
+size_t GetLine() {
+    // reads a line of user input into MEMORY
+    char c;
+    size_t ptr = stack;
+    do {
+        c = getchar();
+        MEMORY[stack++] = c;
+    } while (c != '\n');
+    MEMORY[stack++] = 0;
+    return ptr;
+}
+
+size_t GetVerbatim(size_t start) {
+    // Verbatim words are words that start with {
+    // Braces nest and can be escaped
+    unsigned int level = 0; // first char is {
+    size_t ptr = stack;
+    char c;
+    do {
+        c = MEMORY[start++];
+        // TODO: implement \-escaping
+        if(c == '{') level++;
+        if(c == '}') level--;
+        MEMORY[stack++] = 0;
+    } while(c != 0 && level > 0);
+    MEMORY[stack++] = 0;
+    return ptr;
+}
+
+size_t GetWord(size_t start) {
+    // Start indicates a memory address
+    // Returns a single "word"
+    // Rules of tcl words: [] (and $) work everywhere
+    // having { at the start means that the string is verbatim
+    // {} can be nested
+    // [] is command substitution: essentially calling eval
+    if(MEMORY[start] == '{') return GetVerbatim(start);
+
+    int quote = MEMORY[start] == '"';
+
+    char c;
+    size_t ptr = stack;
+    do {
+        c = MEMORY[start++];
+        // TODO: implement [] and maybe $
+        if(c == '\\') c = MEMORY[start++];
+        // TODO: implement 'smarter' escaping, e.g. \n
+        MEMORY[stack++] = c;
+    } while(c != '"' || (quote && c <= ' '));
+    return ptr;
+}
+
+int main() {
+
+}

sectcl.nasm

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+; x86-16 BIOS bootloader
+[BITS 16]
+[ORG 0x7C00]
+; jmp 0x7C00:start
+start:
+
+call GetChar
+jmp start
+
+; REGISTERS
+;       SP: 'top of memory'
+;	BP: points to variable map
+;	others: general purpose
+GetChar:
+xor     AX,AX			; clear AH
+int     0x16			; read key via BIOS
+; read key is now in AL
+; fallthrough to PutChar to echo read key
+
+PutChar:
+mov	AH,0xe		; TTY mode
+int	0x10		; print character in AL
+cmp     AL, 13          ; if \r, print \r\n and return \n
+jne     .ret
+mov     AL, 10
+call    PutChar
+.ret:   ret
+
+
+; fill up sector, add boot signature
+TIMES 510 - ($ - $$) db 0
+DW 0xAA55