C »ã±à»ìºÏ±à³Ì

As is Known to us,the function Main is the entry point of all programs.Therefore, we are usually neglecting all that we don't do,which makes us not understanding it more clearly.Now there is a sample arm program which will provide something that opration system usually do.
asm:
    IMPORT main
    area test,CODE,READONLY
    ENTRY
    bl start
start
    bl main
C:
#define rGPBCON    (*(volatile unsigned *)0x56000010) //Port B control
#define rGPBDAT    (*(volatile unsigned *)0x56000014) //Port B data
#define rGPBUP     (*(volatile unsigned *)0x56000018) //Pull-up control B
int main(int argc, char *argv[])
{
 unsigned int temp = 0x0e;
 rGPBCON = 0x00555555;
 rGPBUP = 0xffff;
 rGPBDAT = 0XE1F; 
 return 0;
}
The code very sample,but it is very useful.