C Programming Basics

Introduction to Programming

• A computer program is a set of instructions given to a computer to perform a specific task.
• IDE stands for Integrated Development Environment; it facilitates programmers in writing, testing, and executing computer programs.
• A text editor is software for writing and editing computer programs; all IDEs have their own specific text editors.
• Program output is seen after saving, building, and running the program file.
• A computer programmer is someone skilled in writing computer programs and writes code for various software applications.
• A compiler is software that converts high-level programming language into machine language.
• Reserved words or keywords are predefined words in a programming language with specific meanings already known to the compiler.
• Comments in a C program are ignored by the compiler and are used to help programmers understand the code.
• Comments facilitate understanding code and can help understand code over time.

Constants and Variables

• Constants are values that cannot be changed during program execution.
• Types of constants include integer, real, and character constants.
• Examples of constants are 5, 75.7, and 1500.
• A variable is a name given to a memory location where data is stored; its value can be changed.
• Each variable must have a unique name or identifier.
• Variable names can only contain letters, digits, and underscores.
• A variable name must start with a letter or an underscore, but not a digit.
• Variable initialization is assigning a value to a variable for the first time.
• The C language allows initialization at declaration or later: Data_type variable_name = value;.
• Single-line comments start with //, and multi-line comments start with /* and end with */.
• Syntax refers to the set of rules that govern how to write an accurate program in a programming language.
• char declares character type variables, while int is an integer data type used to store integer values.

User Interaction

• printf() is a built-in C function to display output on the screen, with the syntax printf("format string", argument1, argument2, ...);.
• Format specifiers specify the format of data types during input and output operations and are preceded by %.
• %f is for float, and %c is for char.
• scanf() is a built-in C function to take input from the user into variables, specifying the expected data type with a format specifier.
• Syntax: int scanf( const char *format, ... );.
• A statement terminator in C is a semicolon (;), identifying the end of a line.
• getch() reads a character from the user without displaying it on the screen and holds program execution.
• Escape sequences in printf() control output behavior.
• Escape sequence \n moves the cursor to the next line, while \t moves the cursor to the next tab stop.
• Assignment operators assign values to variables, using the equal sign (=) in C.
• Arithmetic operators perform arithmetic operations on data.
• The modulus operator (%) gives the remainder.
• There are also multiplication, subtraction, and division operators
• Logical operators perform operations on Boolean expressions, producing a Boolean result.
• Examples include logical AND (&&), OR (||), and NOT (!).
• AND Operator: False && False = False, False && True = False, True && False = False, True && True = True
• OR Operator: False || False = False, False || True = True, True || False = True, True || True = True
• NOT Operator: !True = False, !False = True

Operators

• Relational operators compare two values to determine relationships like equality, inequality, or relative size.
• Unary operators apply to a single operand, such as logical NOT (!) or sign operators (-).
• Binary operators require two operands, like arithmetic and relational operators.
• The assignment operator (=) assigns a value, while the equality operator (==) checks for equality.
• The double equal operator (==) checks if both the left and right operands are equal.
• Precedence determines the order in which operations are performed. Higher precedence operators are evaluated first, and lower precedence operators are evaluated last.
• Parenthesis () have the highest precedence, and assignment operators have the lowest.

Conditional Logic

• Control statements manage the flow of execution in a program.
• Control statements include sequential, selection, and repetition control statements.
• Sequential control: statements are executed in the order they appear.
• Selection statements decide which statement to execute based on a condition.
• They include if statements and else statements
• An if statement executes code if a condition is true.
• Syntax: if (condition) { Associate code }
• If is a keyword followed by a condition inside parentheses. The associated code is a valid C language set of statement. The condition can be valid expression.
• if else executes one set of statements if a condition is true and another if it's false.
• Syntax: if (condition) { Associate code } else { Associate code }
• A block or compound statement is a group of multiple instructions enclosed in braces.
• Nested selection structure contains if or if else statements inside other if or else blocks.
• A condition can be any expression, including arithmetic, relational, or logical expressions.
• Conditional logic involves making decisions based on conditions, performing specific tasks when conditions are met.

Data and Repetition

• A data structure organizes data for efficient use.
• An array is a data structure that can hold multiple values of the same data type; all stored value is saved in the memory.
• Array initialization is assigning values to an array for the first time, either at declaration or later.
• Example: Float height [7] = {5.7, 6.2, 5.9, 6.1, 5.0, 5.5, 6.2}
• A for loop repeats a block of code a specific number of times.
• The syntax: For (initialization; condition; increment or decrement) { Statements to be executed repeatedly }
• A nested loop is a loop inside another loop.
• Syntax:

 For (initialization; condition; increment) {
    For (initialization; condition; increment) { // statement of inside loop }
     // statements of outer loop
}

• Array declaration specifies the array name, data type, and size.
• Three parts: type, name, and size.
• Syntax: Data-type array-name [array-size];
• A loop executes a block of statements repeatedly until a condition is met.
• Loops save time and minimize errors when performing repetitive tasks.
• Types of loops in C: for loop, while loop, and do-while loop.
• An iteration is a single execution of a loop.
• Initializing an array at declaration avoids needing to initialize each element one by one.
• Array elements are accessed using their index number with the array name: array_name[index].

Function

• A good problem-solving approach divides a problem into smaller parts and then integrates the solutions.
• A function is statements performing a particular task.
• For example: printf
• Functions promote code reusability and separation of tasks.
• Types of functions include built-in and user-defined functions.
• Built-in functions are available in C's standard library.
• User-defined functions are functions defined by the programmer.
• Examples of these are sum, average, and square
• Parameters are variables defined during function declaration, used to receive arguments.
• Arguments are the values passed when a function is called.
• Function signature defines the input and output of a function.
• Structure:

Function identifier
Return_type function_name (data_type1, data_type2,.....data_typeN);
Dada type of return value
Dada type of function parameters

• Defining a function means describing how it performs its assigned task.
• General structure of a function: Return_type function_name (data_type var1, data_type var2,.....data_type varN) { Body of the function }
• The body of a function is the set of statements that execute the function's task.
• Inside a function, return sends a value back to the calling function.
• A function is called to perform its programmed task.
• The general structure to call a function: Function_name (value1, value2,...value N);
• Reusability reuses the same function multiple times.