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Summary - Strings

Combine strlen, strcpy and strcmp to write a name search app.

Summary: Strings

In this group you saw how strings work in C. Strings are char arrays terminated by the null character '\0'. String literals "..." add the null automatically.

Functions from <string.h>:

  • strlen: letter count
  • strcpy: copy to destination
  • strcat: append to destination
  • strcmp: compare (0 = equal)

Now let's combine everything in one task.

Practice Print the string length

Define a char array with the "Welcome" literal. Find the letter count with strlen and print with printf %zu. Output should be 7.

Starter code

main.c
#include <stdio.h>
#include <string.h>

int main(void) {
    /* define char array with "Welcome" */
    /* strlen for length and printf %zu to print */
    return 0;
}

Sample solution

main.c
#include <stdio.h>
#include <string.h>

int main(void) {
    char s[] = "Welcome";
    printf("%zu\n", strlen(s));
    return 0;
}

Expected output

7

Questions and answers

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

1 Which function tests whether two strings are equal?

  • strcmp Correct answer
  • strcpy
  • strlen
  • strcat

Explanation: strcmp returns 0 when the strings are equal.

2 strcpy parameter order

Question 
strcpy(____, src);  /* dst is destination, src is source */
Answer 
strcpy(dst, src);  /* dst is destination, src is source */

Explanation: First parameter is destination (dst), second is source (src).

3 Function purposes

Term Meaning
strlen letter count
strcpy copy
strcat append
strcmp compare

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