Save the environment in which a function call was made
typedef int __near jmp_buf[3];
int __far setjmp(jmp_buf env);
Calling setjmp returns 0. When longjmp is used for a non-local jump, the return value is in the second parameter, val. However, 1 is returned if val is 0.
This function sets env as the destination for a non-local jump. In addition, the environment in which setjmp was run is saved to env.