C programming notess

• C Programming

  Combination of low level (assembly) and high-level programming languages, can be used to write applications and interact with low-level system memory and hardware, can be written on practically any operating system and even works in most handheld devices
• C

  General-purpose programming language created by Dennis Ritchie at the Bell Laboratories in 1972
• C is a very popular language, despite being old
• Reason for C's popularity

  It is a fundamental language in the field of computer science
• C is strongly associated with UNIX, as it was developed to write the UNIX operating system
• Why learn C

  • One of the most popular programming languages in the world
  • If you know C, you will have no problem learning other popular programming languages such as Java, Python, C++, C#, etc, as the syntax is similar
  • C is very fast, compared to other programming languages, like Java and Python
  • C is very versatile; it can be used in both applications and technologies
• Difference between C and C++

  • C++ was developed as an extension of C, and both languages have almost the same syntax
  • The main difference between C and C++ is that C++ support classes and objects, while C does not
• C syntax

  1. #include <stdio.h>

  2. int main() {

  3. printf("Hello World!");

  4. return 0;

  5. }
• #include <stdio.h>

  Header file library that lets us work with input and output functions, such as printf() (used in line 4). Header files add functionality to C programs.
• C ignores white space
• main()

  A function. Any code inside its curly brackets {} will be executed.
• printf()

  A function used to output/print text to the screen
• return 0 ends the main() function
• Computer program

  A list of "instructions" to be "executed" by a computer
• Statements

  Programming instructions in a programming language
• It is important that you end the statement with a semicolon ;
• C Output (Print Text)

  1. #include <stdio.h>

  2. int main() {

  3. printf("Hello World!");

  4. return 0;

  5. }
• Double Quotes

  When you are working with text, it must be wrapped inside double quotations marks ""
• New Lines

  1. #include <stdio.h>

  2. int main() {

  3. printf("Hello World!\n");

  4. printf("I am learning C.");

  5. return 0;

  6. }
• Newline character (\n)

  Forces the cursor to change its position to the beginning of the next line on the screen, resulting in a new line
• Other valid escape sequences

  • \t - Creates a horizontal tab
  • \\ - Inserts a backslash character (\)
  • \" - Inserts a double quote character
• Comments in C

  Can be used to explain code, and to make it more readable. Can also be used to prevent execution when testing alternative code
• Single-line Comments

  Start with two forward slashes (//) and any text between // and the end of the line is ignored by the compiler
• Multi-line Comments

  Start with /* and ends with */. Any text between /* and */ will be ignored by the compiler
• Variables

  Containers for storing data values, like numbers and characters
• Types of variables in C

  • int - stores integers (whole numbers), without decimals
  • float - stores floating point numbers, with decimals
• char

  Stores single characters, such as 'a' or 'B'. Characters are surrounded by single quotes
• Declaring (Creating) Variables

  type variableName = value;
• Where type is one of C types (such as int), and variableName is the name of the variable (such as x or myName). The equal sign is used to assign a value to the variable.
• Output Variables

  To output variables in C, you must get familiar with something called "format specifiers", which you will learn about in the next chapter.
• Format Specifiers

  Format specifiers are used together with the printf() function to tell the compiler what type of data the variable is storing. It is basically a placeholder for the variable value.
• Outputting variables

  • int myNum = 15; printf("%d", myNum); // Outputs 15
  • int myNum = 15; float myFloatNum = 5.99; char myLetter = 'D'; printf("%d\n", myNum); printf("%f\n", myFloatNum); printf("%c\n", myLetter);
• Outputting variables

  • int myNum = 15; char myLetter = 'D'; printf("My number is %d and my letter is %c", myNum, myLetter);
• Changing Variable Values

  Assign new value to overwrite previous value
• Changing Variable Values

  • int myNum = 15; myNum = 10; // Now myNum is 10
  • int myNum = 15; int myOtherNum = 23; myNum = myOtherNum; // myNum is now 23, instead of 15
• Adding Variables Together

  int x = 5; int y = 6; int sum = x + y;
• Declaring Multiple Variables

  • int x = 5, y = 6, z = 50; printf("%d", x + y + z);
  • int x, y, z; x = y = z = 50; printf("%d", x + y + z);
• C Variable Names (Identifiers)

  All C variables must be identified with unique names. These unique names are called identifiers.
• It is recommended to use descriptive names in order to create understandable and maintainable code
• Rules for naming variables

  • Names can contain letters, digits and underscores
  • Names must begin with a letter or an underscore (_)
  • Names are case-sensitive (myVar and myvar are different variables)
  • Names cannot contain whitespaces or special characters like !, #, %, etc.
  • Reserved words (such as int) cannot be used as names