Nested function calls

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Function calls can be nested. Consider the following code.

The calls and returns work as message passing systems where a routines saves what it is doing on the stack, calls the routine (which may save what it is doing on the stack, etc.) and then each called routine returns and the caller resumes what it is doing.

Here is a visualization of the code below.

Nested function calls

Here is the C code.

#include <stdio.h>

void f3(int x1) {
	printf("\t\t\t(begin f3 x1=%d)\n",x1);
	printf("\t\t\t(f3 x1=%d , does nothing more)\n",x1);
	printf("\t\t\t(end f3 x1=%d)\n",x1);
	}

void f2(int x1) {
	printf("\t\t(begin f2 x1=%d)\n",x1);
	f3(3*x1);
	printf("\t\t(end f2 x1=%d)\n",x1);
	}

void f1(int x1) {
	printf("\t(begin f1 x1=%d)\n",x1);
	f2(2*x1);
	printf("\t(end f1 x1=%d)\n",x1);
	}

int main() {
	printf("(begin main)\n");
	f1(1);
	printf("(end main)\n");
	return 0;
	}

Here is the output of the C code.

(begin main)
	(begin f1 x1=1)
		(begin f2 x1=2)
			(begin f3 x1=6)
			(f3 x1=6 , does nothing more)
			(end f3 x1=6)
		(end f2 x1=2)
	(end f1 x1=1)
(end main)

Here is the C code.

#include <stdio.h>

void g3(int y3) {
	printf("\t\t\t(begin g3 y3=%d)\n",y3);
	printf("\t\t\t(g3 y3=%d , does nothing more)\n",y3);
	printf("\t\t\t(end g3 y3=%d)\n",y3);
	}

void g2(int y2) {
	printf("\t\t(begin g2 y2=%d)\n",y2);
	g3(3*y2);
	printf("\t\t(end g2 y2=%d)\n",y2);
	}

void g1(int y1) {
	printf("\t(begin g1 y1=%d)\n",y1);
	g2(2*y1);
	printf("\t(end g1 y1=%d)\n",y1);
	}

int main() {
	printf("(begin main)\n");
	g1(1);
	printf("(end main)\n");
	return 0;
	}

Here is the output of the C code.

(begin main)
	(begin g1 y1=1)
		(begin g2 y2=2)
			(begin g3 y3=6)
			(g3 y3=6 , does nothing more)
			(end g3 y3=6)
		(end g2 y2=2)
	(end g1 y1=1)
(end main)