Talk:Low-level programming language

Examples

This page could use some examples. Thehotelambush 16:09, 30 July 2007 (UTC)[reply]

Example - a function that calculates the nth Fibonacci number.

First, in C [3rd generation]:

unsigned int fib(unsigned int n)
{
    if (n <= 0)
        return 0;
    else if (n <= 2)
        return 1;
    else {
        int a,b,c;
        a = 1;
        b = 1;
        while (1) {
            c = a + b;
            if (n <= 3) return c;
            a = b;
            b = c;
            n--;
        }
    }
}

The same function, but converted to x86 assembly language, specifically MASM, using the __cdecl calling convention [2nd generation]:

fib:
    mov edx, [esp+8]
    cmp edx, 0
    ja @f
    mov eax, 0
    ret
    
    @@:
    cmp edx, 2
    ja @f
    mov eax, 1
    ret
    
    @@:
    push ebx
    mov ebx, 1
    mov ecx, 1
    
    @@:
        lea eax, [ebx+ecx]
        cmp edx, 3
        jbe @f
        mov ebx, ecx
        mov ecx, eax
        dec edx
    jmp @b
    
    @@:
    pop ebx
    ret

Note:

@f refers to the closest following @@: label.

@b refers to the closest preceding @@: label.

I deliberately did not use proc.

And here is the final x86 machine code [1st generation]:

8B542408 83FA0077 06B80000 0000C383
FA027706 B8010000 00C353BB 01000000
B9010000 008D0419 83FA0376 078BD98B
C84AEBF1 5BC3

For comparison purposes, here is a disassembly listing:

00401000                    fib:
00401000 8B542408               mov     edx,[esp+8]
00401004 83FA00                 cmp     edx,0
00401007 7706                   ja      loc_0040100F
00401009 B800000000             mov     eax,0
0040100E C3                     ret
0040100F                    loc_0040100F:
0040100F 83FA02                 cmp     edx,2
00401012 7706                   ja      loc_0040101A
00401014 B801000000             mov     eax,1
00401019 C3                     ret
0040101A                    loc_0040101A:
0040101A 53                     push    ebx
0040101B BB01000000             mov     ebx,1
00401020 B901000000             mov     ecx,1
00401025                    loc_00401025:
00401025 8D0419                 lea     eax,[ecx+ebx]
00401028 83FA03                 cmp     edx,3
0040102B 7607                   jbe     loc_00401034
0040102D 8BD9                   mov     ebx,ecx
0040102F 8BC8                   mov     ecx,eax
00401031 4A                     dec     edx
00401032 EBF1                   jmp     loc_00401025
00401034                    loc_00401034:
00401034 5B                     pop     ebx
00401035 C3                     ret

Alksentrs (talk) 23:57, 16 February 2008 (UTC)[reply]

Absolute terms

I've always known low-level and high-level programming languages to be absolute terms. The former refers to programming languages that provide no abstraction from the instructions that the processor implements, this is binary code (maybe written in hexadecimal), and assembler language, which is a mnemonic for the binary code and is assembled. The latter refers to programming languages that can be used independently of the processor because there is a software layer that abstracts that detail (something an assembler does not do), as a compiler or an interpreter.

The crisp and absolute difference between low-level programming languages and high-level programming languages, for what I knew, is that the code is done for a specific hardware (or group of them) as may be the x86 group of processors, or it is done for a software (or group of them) as is the group of C compilers.

Unfortunately I haven't been able to find references as this is more a terminological matter than a informatics matter, that's why I've required the citation (as there may be one). All that I got by now is this a definition in the webopedia[1].

Kind regards.