Compilation process in C - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to include the standard input-output header.

C

#include [1]

int main() {
    printf("Hello, world!\n");
    return 0;
}

Drag options to blanks, or click blank then click option'

A<math.h>

B<stdlib.h>

C<string.h>

D<stdio.h>

Attempts:

3 left

💡 Hint

Common Mistakes

Including instead of causes undefined reference to printf.

Forgetting the angle brackets around the header name.

The <stdio.h> header is required for the printf function.

2fill in blank

medium

Complete the command to compile a C file named program.c using gcc.

C

gcc [1] -o program

Drag options to blanks, or click blank then click option'

Aprogram

B-c

Cprogram.c

D-o

Attempts:

3 left

💡 Hint

Common Mistakes

Using the output file name instead of the source file.

Confusing the -o option with the source file.

The source file to compile is program.c. The -o option specifies the output file name.

3fill in blank

hard

Fix the error in the compilation command to generate only the object file.

C

gcc -o program.o [1] program.c

Drag options to blanks, or click blank then click option'

A-c

Bprogram.o

Cprogram.c

D-o

Attempts:

3 left

💡 Hint

Common Mistakes

Placing -o before -c incorrectly.

Omitting the -c option when only compiling.

The -c option tells gcc to compile only and not link. It should come before the source file.

4fill in blank

hard

Fill both blanks to complete the compilation stages in order.

C

gcc -E [1] -o [2]

Drag options to blanks, or click blank then click option'

Aprogram.c

Bprogram.i

Cprogram.o

Dprogram.s

Attempts:

3 left

💡 Hint

Common Mistakes

Using the object file .o or assembly file .s as output for preprocessing.

Confusing input and output file names.

The -E option runs the preprocessor on program.c and outputs the result to program.i.

5fill in blank

hard

Fill all three blanks to complete the compilation pipeline: preprocessing, compiling, and assembling.

C

gcc -E [1] -o [2]
gcc -S [2] -o [3]

Drag options to blanks, or click blank then click option'

Aprogram.c

Bprogram.i

Cprogram.s

Dprogram.o

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up file extensions for each stage.

Using object file .o instead of assembly .s for the compile output.

First, preprocessing program.c creates program.i. Then compiling program.i creates assembly program.s.

Practice

1. Which of the following is the correct order of steps in the C compilation process?

easy

A. Preprocessing, Compilation, Assembly, Linking

B. Compilation, Preprocessing, Linking, Assembly

C. Linking, Assembly, Compilation, Preprocessing

D. Assembly, Linking, Preprocessing, Compilation

Solution

1. Step 1: Understand the compilation stages

   The C compilation process starts with preprocessing, where directives like #include are handled.

2. Step 2: Follow the correct sequence

   After preprocessing, the code is compiled into assembly, then assembled into machine code, and finally linked to create an executable.

3. Final Answer:

   Preprocessing, Compilation, Assembly, Linking -> Option A

4. Quick Check:

   Compilation steps order = A [OK]

Hint: Remember: Preprocess first, then compile, assemble, and link [OK]

Common Mistakes:

• Mixing up the order of compilation steps
• Thinking linking happens before assembly
• Confusing preprocessing with compilation

2. Which of the following commands runs the preprocessor only in GCC?

easy

A. gcc -o file file.c

B. gcc -c file.c

C. gcc -S file.c

D. gcc -E file.c

Solution

1. Step 1: Identify GCC flags for compilation steps

   The flag '-E' tells GCC to run only the preprocessor and output the result.

2. Step 2: Understand other flags

   '-c' compiles to object code, '-S' compiles to assembly, and '-o' specifies output file name.

3. Final Answer:

   gcc -E file.c -> Option D

4. Quick Check:

   Preprocessor only = gcc -E [OK]

Hint: Use gcc -E to run only the preprocessor [OK]

Common Mistakes:

• Confusing -E with -c or -S
• Using -o without understanding its purpose
• Assuming -c runs the preprocessor only

3. What will be the output of the following commands sequence?

gcc -c file.c
gcc file.o -o program
./program

Assuming file.c contains a valid main function that prints "Hello".

medium

A. Compilation error

B. Hello

C. Linker error

D. No output

Solution

1. Step 1: Understand the commands

   'gcc -c file.c' compiles source to object file without linking. 'gcc file.o -o program' links object file to create executable.

2. Step 2: Run the executable

   Running './program' executes the compiled program, which prints "Hello" as per the source code.

3. Final Answer:

   Hello -> Option B

4. Quick Check:

   Compile, link, run = Hello output [OK]

Hint: Compile with -c, then link and run to see output [OK]

Common Mistakes:

• Expecting output without linking
• Confusing compile-only with full build
• Not running the executable after linking

4. Given the code int main() { printf("Hi"); return 0; }, which error occurs if you compile with gcc file.c but forget to include #include <stdio.h>?

medium

A. Preprocessing error

B. Linker error

C. Compilation warning or error about implicit declaration

D. No error, program runs fine

Solution

1. Step 1: Identify missing header impact

   Without #include <stdio.h>, the compiler does not know the prototype of printf, causing implicit declaration warning or error.

2. Step 2: Understand error type

   This is a compilation warning or error, not a linker or preprocessing error.

3. Final Answer:

   Compilation warning or error about implicit declaration -> Option C

4. Quick Check:

   Missing stdio.h = compilation warning/error [OK]

Hint: Always include stdio.h for printf to avoid compile errors [OK]

Common Mistakes:

• Thinking it's a linker error
• Assuming no error occurs
• Confusing preprocessing errors with compilation errors

5. You have two C files: main.c and utils.c. You compile them separately with gcc -c main.c and gcc -c utils.c. What is the correct command to create an executable named app linking both object files?

hard

A. gcc main.o utils.o -o app

B. gcc main.c utils.c -c -o app

C. gcc -o app main.c utils.c

D. gcc -c main.o utils.o -o app

Solution

1. Step 1: Understand separate compilation

   Compiling with '-c' creates object files (.o) without linking.

2. Step 2: Link object files to create executable

   Use 'gcc main.o utils.o -o app' to link object files into executable named 'app'.

3. Final Answer:

   gcc main.o utils.o -o app -> Option A

4. Quick Check:

   Link object files with gcc -o app [OK]

Hint: Link .o files with gcc -o executable_name [OK]

Common Mistakes:

• Using -c flag during linking
• Trying to compile .o files directly
• Mixing source and object files incorrectly