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Project design

Design the structure of the calculator project and write the skeleton code.

Project: Calculator

In this 5-lesson project you'll build a calculator. Each lesson adds one piece, and by the final lesson you'll have a complete app.

You'll use:

  • int main(void) and printf
  • add, subtract, multiply, divide functions
  • if for a divide-by-zero check
  • while and switch for a menu loop

Ready? Let's start.

Project plan

We'll build the calculator piece by piece:

  1. First the skeleton: write a header with main and printf
  2. Then add add and subtract functions
  3. Add multiply and divide functions
  4. Build a menu with while and switch
  5. Put everything together

Each lesson will include the previous lesson's code, so you end up with a working app.

Practice Write the first skeleton

Write a C program: #include <stdio.h>, int main(void), and print Calculator with printf.

Starter code

main.c
// Write the calculator skeleton

Sample solution

main.c
#include <stdio.h>

int main(void) {
    printf("Calculator");
    return 0;
}

Expected output

Calculator

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 Which is the correct signature for add?

  • add(int a, int b)
  • int add(a, b)
  • void add(int a, int b)
  • int add(int a, int b) Correct answer

Explanation: int add(int a, int b) takes two ints and returns an int.

2 Second parameter

Question 
int add(int a, ____) { return a + b; }
Answer 
int add(int a, int b) { return a + b; }

Explanation: In int add(int a, int b) the second parameter is int b.

3 Match the functions

Term Meaning
add Addition
subtract Subtraction
multiply Multiplication
divide Division

All lessons in Beginner

1 C basics

  1. What is C?
  2. Your first program
  3. Compile and run
  4. Comments
  5. printf and escapes
  6. Summary - C basics

2 Variables

  1. Declaring variables
  2. Variable assignment
  3. const
  4. Variable scope
  5. typedef
  6. Summary - Variables

3 Data types

  1. Integer types
  2. Floating-point types
  3. char
  4. sizeof
  5. Type conversion
  6. Summary - Data types

4 Project: Calculator

  1. Project design
  2. Add and subtract
  3. Multiply and divide
  4. Menu loop
  5. Putting it together

5 Operators

  1. Arithmetic operators
  2. Assignment operators
  3. Comparison operators
  4. Logical operators
  5. Bitwise operators
  6. Summary - Operators

6 I/O

  1. printf formatting
  2. scanf
  3. Multiple inputs
  4. getchar and putchar
  5. puts and fputs
  6. Summary - I/O

7 Conditionals

  1. The if statement
  2. else and else if
  3. The switch statement
  4. The ternary operator
  5. Nested conditionals
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. The do-while loop
  4. break and continue
  5. Nested loops
  6. Summary - Loops

9 Project: Shopping cart

  1. Cart design
  2. Adding products
  3. Calculating totals
  4. Listing the cart
  5. Putting it together

10 Arrays

  1. Declaring arrays
  2. Array access
  3. Array size
  4. Multidimensional arrays
  5. Arrays and loops
  6. Summary - Arrays

11 Strings

  1. String basics
  2. String literals
  3. strlen
  4. strcpy and strcat
  5. strcmp
  6. Summary - Strings

12 Functions

  1. Defining functions
  2. Return values
  3. Parameters
  4. Function prototypes
  5. Recursion
  6. Summary - Functions

13 Pointer basics

  1. What is a pointer?
  2. The & address operator
  3. Pointer dereference
  4. NULL
  5. Pointer arithmetic
  6. Summary - Pointer basics

14 Arrays and pointers

  1. Array name as pointer
  2. Pointer to array
  3. Passing arrays to functions
  4. Pointer loop
  5. Multidim array pointer
  6. Summary - Arrays and pointers

15 Project: To-do CLI

  1. Task model
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Putting it together

16 String functions

  1. strchr
  2. strstr
  3. strtok
  4. sprintf
  5. sscanf
  6. Summary - String functions

17 Structs

  1. Defining structs
  2. Using structs
  3. typedef struct
  4. Array of structs
  5. Nested structs
  6. Summary - Structs

18 Memory and stack

  1. Stack and heap
  2. Automatic storage
  3. malloc
  4. free
  5. calloc and realloc
  6. Summary - Memory and stack

19 Preprocessor

  1. #define
  2. #include
  3. Conditional compilation
  4. Macro functions
  5. Header files
  6. Summary - Preprocessor

20 Beginner final

  1. Project design
  2. Data model
  3. Functions
  4. Memory management
  5. Putting it together