5. A program to print out 640d hex addresses with their bytes on a single 66-line page, in ten columns of 64d entries each. It is useful for studying machine code programs, whether in the ROM, one's own, or obtained from elsewhere. It requires an eighty-column printer. 5 REM "hexpt 10 REM "Machine code display. 20 REM "Functions: h$() converts decimal to hex, a$() and b$() form the hi and lo hex digits of a byte given in decimals, z$() forms a 2-byte number given in decimals into four hex digits. 30 DEF FN h$(x) = CHR$ (48*(x<10) + 55*(x>9) + x) 40 DEF FN a$(x) = FN h$(x - 16*INT (x/16)) 50 DEF FN b$(x) = FN h$(INT (x/16)) 60 DEF FN z$(x) = FN a$(INT (x/256)) + FN b$(INT (x/256)) + FN a$(x - 256*INT (x/256)) + FN b$(x - 256*INT (x/256)) 1000 REM "Initial prompt: 1100 CLS: PRINT AT 7,3; "Prints out machine code in"; AT 8,6; "hexadecimal numbers."; AT 10,6; "640 bytes per page.": INPUT "Input start no (decimal): ";g: INPUT "How many pages? ";p: LET z = g + 640*p - 1 1199 REM "Page printing loop: subr 2100 prints entry a. 1200 FOR f=g TO g+63: FOR c=0 TO 9: REM "Prints entry in line f, column c+1: ta, tb are tabsettings. 1300 LET a= f + 64*c: LET ta= 8*c: LET tb= 8*c + 5: GO SUB 2100: NEXT c: NEXT f: LPRINT ''': LET g= g + 640: IF g < z THEN GO TO 1200 1400 STOP 2000 REM "Subr to print address and contents of entry a. 2100 LPRINT TAB ta; FN z$(a); TAB tb; FN z$(PEEK a)(3 TO);: RETURN 9999 SAVE d1 "hexpt" LINE 1000 There are several commercially available "disassembler" programs, which read machine code and print out assembly language; such programs are usually mostly in m/c and quite complex.
