The setjmp.h header file provides a means of saving and restoring a processor state. The setjmp.h functions are typically used for programming error and low-level interrupt handlers.

• The function "setjmp" saves the current calling environment-the current processor state-in its jmp_buf argument. The jmp_buf type, an array, holds the processor program counter, stack pointer, and relevant data and address registers.
• The function "longjmp" restores the processor to its state at the time of the last setjmp() call. In other words, longjmp() returns program execution to the last setjmp() call if the setjmp() and longjmp() pair use the same jmp_buf variable as arguments.