Can someone explain why the code prints "HelloWorld" and not "HelloWorldThere" ? Also why does it print anything at all as there are no conditions in if or switch statements ? Here is the code:
#include <stdio.h> int main() { int a, b; if(printf("Hello")) switch(printf("World")) while(printf("There")) { return 0; } } Pretty straightforward: printf("Hello") returns 5 (the number of characters written). 5 is not 0, so it's considered "true" for the purposes of the if, so then printf("World") also returns 5, the switch looks for a case 5:, doesn't find one, and stops there.
For starters, let's consider what the function printf returns. From the C Standard
3 The
printffunction returns the number of characters transmitted, or a negative value if an output or encoding error occurred.
So the condition of this if statement
if(printf("Hello")) evaluates to true because printf() returns a non-zero value.
Then this switch statement
switch(printf("World")) is evaluated.
Now let's consider how the switch statement works. From the C Standard
4 A
switchstatement causes control to jump to, into, or past the statement that is the switch body, depending on the value of a controlling expression, and on the presence of a default label and the values of any case labels on or in the switch body. A case or default label is accessible only within the closest enclosing switch statement.
As the body statement of the switch statement does not have a label (including the default label) then the control is passed past the body statement. That is, the while statement (that is a body statement of the switch statement) is not executed.
If you want to get the expected by you result then for example insert the label default.
#include <stdio.h> int main() { if(printf("Hello")) switch(printf("World")) default: while(printf("There")) { return 0; } } In this case the program output is
HelloWorldThere Or use a null-statement as the body statement of the switch statement.
#include <stdio.h> int main() { if(printf("Hello")) switch(printf("World")); // <== while(printf("There")) { return 0; } } 
printfreturns.switchstatement too ... Your code is totally a non-sense.switch: "If expression evaluates to a value that doesn't match any of the case: labels, and the default: label is not present, none of the switch body is executed." -- nocaselabels, so nothing to match the expression, and nodefaultlabel, so nothing happens.