Constants in C Language

There is such a C program:

 

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The results of the final program can be easily guessed, but there is also a useful knowledge: 0xfe is a constant, and the final translation into assembly language is an immediate number, which is stored in registers. This indicates that this constant occupies a word length, and the upper limit of less than one word length is eventually extended to 0. Based on this principle, we can write a mask program that does not depend on a specific machine.

1 # include <stdio. h> 2 3 int main () 4 {5 char hex1 = 0xfe; 6 int hex2 = 0 xfefe; 7 8 char hex3 = hex1 & 0xfe; 9 int hex4 = hex2 & 0 xfefe; 10 11 printf ("hex3 = % x, hex4 = % x \ n", hex3, hex4); 12}