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3.4.1 数字常量
数字类型常量就是一个简单的数字，NASM允许使用不同进制的数字。可以使用以下前缀H或X、D或T、Q或O、B和Y，分别表示十六进制（hexadecimal）、十进制(decimal)、八进制(octal)、二进制数（binary）。NASM也支持C语言风格的0x前缀来表示十六进制数，支持Borland Pascal或Motorola汇编器的风格，使用$前缀来表示十六进制数。但要注意在NASM中$有两个功能（见3.1节），因此在表示十六进制数时，$之后要接数字而不能是字母。此外当前NASM接受前缀0h表示十六进制数，0d或0t表示十进制，0o或0q表示八进制，0b或oy表示二进制。请注意，与C语言不同单独的前缀0不能表示八进制常量。
数字常量可以包含_来分割长数字。
以下例子，实际上会产生相同的代码。
mov ax,200 ; decimal
mov ax,0200 ; still decimal
mov ax,0200d ; explicitly decimal
mov ax,0d200 ; also decimal
mov ax,0c8h ; hex
mov ax,$0c8 ; hex again: the 0 is required
mov ax,0xc8 ; hex yet again
mov ax,0hc8 ; still hex
mov ax,310q ; octal
mov ax,310o ; octal again
mov ax,0o310 ; octal yet again
mov ax,0q310 ; octal yet again
mov ax,11001000b ; binary
mov ax,1100_1000b ; same binary constant
mov ax,1100_1000y ; same binary constant once more
mov ax,0b1100_1000 ; same binary constant yet again
mov ax,0y1100_1000 ; same binary constant yet again