Section quiz

Your first C program

Nine questions on what the compiler does, the errors you have now met on purpose, and what printf and scanf will and will not do for you.

Questions are shuffled within each part, and so are the answers. You can retake it as often as you like.

0 of 9 answered

Part 1: How a C program gets built

Question 1

The compiler prints a warning about your program but no error. What has it done?

A.Refused to build, the same as an error, but with gentler wording.B.Built the program anyway. It runs, and it may well do the wrong thing.C.Built the program and automatically corrected the problem it found.D.Built the program and arranged for it to stop if the problem actually occurs.

Question 2

What does #include <stdio.h> actually do?

A.It loads the standard library into memory when your program starts.B.A step before the compiler replaces that line with the text of the header file, which describes printf and its relatives.C.It runs the first time printf is called, and finds printf then.D.It copies the machine code of printf into your file so the compiler can see how printf works.

Question 3

A 400 line C program has a missing semicolon on line 380. You build it and run it. What happens?

A.The whole program runs and quietly skips line 380.B.Nothing runs. The compiler stops, produces no program, and prints a complaint instead.C.Lines 1 to 379 run, then the program stops with an error at line 380.D.The program runs normally and the mistake is reported at the end.

Question 4

Your build fails with a message naming square and containing no file name and no line number. What has gone wrong?

A.You forgot a semicolon somewhere before the call to square.B.The program ran and crashed inside square.C.You spelled square differently in two places, and the compiler is telling you so.D.The linker could not find any code for a function you promised existed and then called.

Part 2: Getting values in and out

Question 5

int n = 5; int got = scanf("%d", &n); is given the input hello. What are got and n afterwards?

A.got is 0 and n is 0, because a failed read clears the variable.B.got is 1 and n is some meaningless number.C.got is 0 and n is still 5.D.got is -1, because any failure returns EOF.

Question 6

You write scanf("%d", n); instead of scanf("%d", &n);. What is the consequence?

A.scanf reads nothing and returns 0, leaving n alone.B.The program refuses to build under any circumstances, so it cannot get as far as running.C.scanf reads the number into n anyway, since it can see which variable you meant.D.scanf treats the number currently in n as an address and writes there, which usually crashes and otherwise corrupts something.

Question 7

You want to read a double from the input. Which is right?

A.scanf("%f", &value), the same specification printf uses for a doubleB.scanf("%d", &value), since %d handles any numberC.scanf("%lf", &value)D.scanf("%lf", value), because a double is already big enough to hold its own address

Question 8

What does printf("%d", 3); printf("%d", 4); put on the screen?

A.34, with no space and no new line.B.Nothing, because neither format string has a \n in it.C.3 4, because printf separates values with a space.D.3 and 4 on two lines, because each printf ends its line.

Question 9

What does printf("%d\n", 7 / 2); print?

A.3.5B.3.500000C.4D.3

9 questions left to answer.