1 ; testdata_64.asm a program to demonstrate data types and values 2 ; assemble: nasm -f elf64 -l testdata_64.lst testdata_64.asm 3 ; link: gcc -m64 -o testdata_64 testdata_64.o 4 ; run: ./testdata_64 5 ; Look at the list file, testdata_64.lst 6 ; no output 7 ; Note! nasm ignores the type of data and type of reserved 8 ; space when used as memory addresses. 9 ; You may have to use qualifiers BYTE, WORD, DWORD or QWORD 10 11 section .data ; data section 12 ; initialized, writeable 13 14 ; db for data byte, 8-bit 15 00000000 FF0111 db01: db 255,1,17 ; decimal values for bytes 16 00000003 FFAB db02: db 0xff,0ABh ; hexadecimal values for bytes 17 00000005 616263 db03: db 'a','b','c' ; character values for bytes 18 00000008 616263 db04: db "abc" ; string value as bytes 'a','b','c' 19 0000000B 616263 db05: db 'abc' ; same as "abc" three bytes 20 0000000E 68656C6C6F0D0A00 db06: db "hello",13,10,0 ; "C" string including cr and lf 21 22 ; dw for data word, 16-bit 23 00000016 3930EFFF2000 dw01: dw 12345,-17,32 ; decimal values for words 24 0000001C FFFFCDAB dw02: dw 0xFFFF,0abcdH ; hexadecimal values for words 25 00000020 6100616261626300 dw03: dw 'a','ab','abc' ; character values for words 26 00000028 68656C6C6F00 dw04: dw "hello" ; three words, 6-bytes allocated 27 28 ; dd for data double word, 32-bit 29 0000002E 15CD5B07F9FFFFFF dd01: dd 123456789,-7 ; decimal values for double words 30 00000036 FFFFFFFF dd02: dd 0xFFFFFFFF ; hexadecimal value for double words 31 0000003A 61000000 dd03: dd 'a' ; character value in double word 32 0000003E 68656C6C6F000000 dd04: dd "hello" ; string in two double words 33 00000046 AF7D2773 dd05: dd 13.27E30 ; floating point value 32-bit IEEE 34 35 ; dq for data quad word, 64-bit 36 0000004A 141A99BE1C000000F9- dq01: dq 123456789012,-7 ; decimal values for quad words 36 00000053 FFFFFFFFFFFFFF 37 0000005A FFFFFFFFFFFFFFFF dq02: dq 0xFFFFFFFFFFFFFFFF ; hexadecimal value for quad words 38 00000062 6100000000000000 dq03: dq 'a' ; character value in quad word 39 0000006A 68656C6C6F5F776F72- dq04: dq "hello_world" ; string in two quad words 39 00000073 6C640000000000 40 0000007A C86BB752A7D0737E dq05: dq 13.27E300 ; floating point value 64-bit IEEE 41 42 ; dt for data ten of 80-bit floating point 43 00000082 4011E5A59932D5B6F0- dt01: dt 13.270E3000 ; floating point value 80-bit in register 43 0000008B 66 44 45 46 section .bss ; reserve storage space 47 ; uninitialized, writeable 48 49 00000000 s01: resb 10 ; 10 8-bit bytes reserved 50 0000000A s02: resw 20 ; 20 16-bit words reserved 51 00000032 s03: resd 30 ; 30 32-bit double words reserved 52 000000AA s04: resq 40 ; 40 64-bit quad words reserved 53 000001EA s05: resb 1 ; one more byte 54 55 SECTION .text ; code section 56 global main ; make label available to linker 57 main: ; standard gcc entry point 58 59 00000000 55 push rbp ; initialize stack 60 61 00000001 8A0425[00000000] mov al,[db01] ; correct to load a byte 62 00000008 8A2425[00000000] mov ah,[db01] ; correct to load a byte 63 0000000F 668B0425[16000000] mov ax,[dw01] ; correct to load a word 64 00000017 8B0425[2E000000] mov eax,[dd01] ; correct to load a double word 65 0000001E 488B0425[4A000000] mov rax,[dq01] ; correct to load a quad word 66 67 00000026 8A0425[00000000] mov al,BYTE [db01] ; redundant, yet allowed 68 0000002D 668B0425[00000000] mov ax,[db01] ; no warning, loads two bytes 69 00000035 8B0425[16000000] mov eax,[dw01] ; no warning, loads two words 70 0000003C 488B0425[2E000000] mov rax,[dd01] ; no warning, loads two double words 71 72 ; mov ax,BYTE [db01] ; error, size miss match 73 ; mov eax,WORD [dw01] ; error, size miss match 74 ; mov rax,WORD [dd01] ; error, size miss match 75 76 ; push BYTE [db01] ; error, can not push a byte 77 00000044 66FF3425[16000000] push WORD [dw01] ; "push" needs to know size 2-byte 78 ; push DWORD [dd01] ; error, can not push a 4-byte 79 0000004C FF3425[4A000000] push QWORD [dq01] ; OK 80 81 ; push eax ; error, wrong size, need 64-bit 82 00000053 50 push rax 83 84 00000054 D90425[46000000] fld DWORD [dd05] ; floating load 32-bit 85 0000005B DD0425[7A000000] fld QWORD [dq05] ; floating load 64-bit 86 87 00000062 BB00000000 mov rbx,0 ; exit code, 0=normal 88 00000067 B801000000 mov rax,1 ; exit command to kernel 89 0000006C CD80 int 0x80 ; interrupt 80 hex, call kernel 90 91 ; end testdata_64.asm