Compilation and execution process in C++ - Step-by-Step Execution

Concept Flow - Compilation and execution process

Write C++ source code

↓

Preprocessing: handle #include, macros

↓

Compilation: convert code to assembly

↓

Assembly: convert assembly to machine code

↓

Linking: combine object files and libraries

↓

Executable file created

↓

Execution: OS loads and runs program

This flow shows how C++ source code is transformed step-by-step into a running program.

Execution Sample

C++

#include <iostream>
int main() {
  std::cout << "Hello!" << std::endl;
  return 0;
}

A simple C++ program that prints 'Hello!' to the screen.

Execution Table

Step	Process	Action	Output/Result
1	Write source code	Create .cpp file with code	Source code file created
2	Preprocessing	Expand #include and macros	Expanded source code
3	Compilation	Convert expanded code to assembly	Assembly code generated
4	Assembly	Convert assembly to machine code	Object file (.o) created
5	Linking	Combine object files and libraries	Executable file created
6	Execution	OS loads executable and runs it	Program runs and prints 'Hello!'
7	Exit	Program ends with return 0	Process terminates normally

💡 Program finishes execution and returns control to OS

Variable Tracker

Variable	Start	After Preprocessing	After Compilation	After Assembly	After Linking	During Execution	Final
source_code	Original code text	Expanded code text	Assembly code	Machine code	Executable file	Loaded in memory	Program ends
output	None	None	None	None	None	"Hello!" printed	"Hello!" printed

Key Moments - 3 Insights

Why do we need preprocessing before compilation?

Preprocessing handles #include and macros so the compiler sees full code without shortcuts, as shown in step 2 of the execution_table.

What is the difference between compilation and assembly?

Compilation translates code to assembly language (step 3), while assembly converts that assembly to machine code (step 4), preparing it for linking.

Why is linking necessary after assembly?

Linking combines all object files and libraries into one executable (step 5), so the program can run as a whole.

Visual Quiz - 3 Questions

Look at the execution_table, what is the output after the linking step?

A Assembly code generated

B Executable file created

C Source code expanded

D Program prints 'Hello!'

💡 Hint

Check row 5 in execution_table under Output/Result column

At which step does the program actually run and print output?

A Execution

B Linking

C Compilation

D Preprocessing

💡 Hint

Look at step 6 in execution_table where the program runs

If the source code has a syntax error, at which step will the process stop?

A Assembly

B Preprocessing

C Compilation

D Linking

💡 Hint

Syntax errors are caught during compilation, see step 3 in execution_table

Concept Snapshot

C++ compilation process:
1. Preprocessing: expands includes/macros
2. Compilation: source to assembly
3. Assembly: assembly to machine code
4. Linking: combine files to executable
5. Execution: OS runs program
Errors usually stop compilation.

Full Transcript

This visual shows how a C++ program goes from source code to running program. First, you write code. Then preprocessing expands includes and macros. Compilation turns code into assembly language. Assembly converts that to machine code in object files. Linking combines these into an executable file. Finally, the OS loads and runs the program, which prints output and ends. Errors like syntax mistakes stop the process during compilation. This step-by-step helps beginners see how code becomes a running program.