Basics of C/C++ Programming

Introduction

Lecturers

Rait Liiv: rait.liiv@itcollege.ee

Janno Tomingas: janno.tomingas@itcollege.ee

C

Practices

Practice 1

Console input/output

1. Write a program, that outputs "Hello, World!"

2. Write a program, that asks the user for a number and then writes the number back to the user

3. Write a simple calculator, that supports addition, subtraction, multiplication and division. The program should ask the user for two numbers and the operation to perform and output the result to the console.

Practice 2

Functions, pointers, out variables, function return values as success/error codes

1. Write a function that adds two integers, outputs the result via an out variable and returns 0 to indicate a successful operation.

Hint:

 int add(int a, int b, int* out)
 {
 }

2. Write a function that swaps two integers and returns 0 to indicate a successful operation.

Hint:

 int swap(int* a, int* b)
 {
 }

3. Write a function that reverses a string and returns 0 to indicate a successful operation.

Hint:

 int reverse(char* string, size_t length)
 {
 }

4. Write a function that sorts an array of ints and returns 0 to indicate a successful operation.

Hint:

 int sort(int* string, size_t length)
 {
 }

Practice 3

File input/output, dynamic memory allocation

1. Write a program that outputs the contents of a text file into the console.

Hint:

Always close the file stream after you are done using it.

Make sure to check for error codes.

2. Write a program that reads the contents of a text file into a dynamically sized array and outputs the information into a new file.

Hint:

Use "fseek", "ftell" and "rewind" to find out how large the buffer should be.

Make sure you have enough room for a null terminator.

Remember to free the allocated memory after calling malloc or calloc.

Make sure to check for error codes.

Practice 4

Dynamic memory allocation continued, structs, .h/.c files

1. Create an implementation of a stack data structure (Stack (abstract data type)) that uses a dynamically allocated array for storage.

• Required functions:
  • init - Initializes stack's variables and allocates required dynamic memory with an initial(default) size,
  • destroy - Frees all allocated memory and optionally resets other stored information for a stack,
  • push - Adds an element to the top of the stack,
  • peek - Gets the top element of the stack,
  • pop - Gets and removes the top element of the stack;

• Describe the stack struct and functions in a separate .h file,
• Implement the functions in a corresponding .c file,
• Test your stack with some operations. Remember to check for edge cases;

Hints:

• How do you know which element to access?
• How do you know if an array is full?
• How should the functions behave when a stack is empty?
• How should the functions behave when a stack is full?
• What will happen if any of the functions are called unexpectedly many times?

Assignment

Write a program that reads values from a file and outputs the result to stdout.

Input

Input file's name is "input.txt".

The file contains index-value pairs of integers on a single line. Integers in a pair are separated with a comma (,) and pairs are separated with a semicolon (;).

All indices between 0 and (count_of_pairs - 1) are guaranteed to be present.

The indices are guaranteed to be unique.

The indices are not guaranteed to appear in an ascending order.

Sample input: 1,4;0,2;2,8

Output

The program should output the changes in values as the index increases.

Output should be printed as comma separated values on a single line to stdout.

For input:

0,1;2,4;1,2

Calculates:

0,1 to 1,2 -> 2 - 1 = 1
1,2 to 2,4 -> 4 - 2 = 2

And outputs:

1,2

Examples

-> 0
0,2 -> 0
1,2;0,1 -> 1
1,4;0,2;2,8 -> 2,4
1,4;0,2;2,-2 -> 2,-6