Question

Possible Duplicate:
Why do I get a segmentation fault when writing to a string?

I have the following program:

char *s     = "abcdf";
char s1[50] = "abcdf";

s1[0] = 'Q';   // Line 1
s[0] = 'P';    // Line 2

Why Line 1 worked correctly and Line 2 caused the program to crash?

Answer 1

Line 2 points to the data section of your executable which is read-only, whereas in line 1, the program initializes s1 array with the given string. This is stored in stack, which you can modify.