Computer Science: Control Structures

• Computer science involves studying computation and information.
• Computer science has both theoretical and practical applications.

Control Structures

• Control structures manage the order of instruction execution.
• Programs that make decisions and repeat actions are enabled by control structures.
• Sequential, selection, and iteration represent the three basic types of control structures.

Sequential Execution

• Instructions are carried out linearly, one after the other.
• In most languages, it is the default execution mode for programs.
• Source code statements are handled in the order they appear.

Selection (Conditional) Statements

• Programs can use selection statements to select execution pathways based on specific conditions.
• Common selection statements include if, else if, and switch.
• An if statement will only run a block of code if the condition is true.
• else if statements check extra conditions if the initial if condition is not met.
• An else statement executes a block of code when none of the conditions are met.
• Based on the value of a variable, switch statements choose a code block to run.

Iteration (Looping) Statements

• Iteration statements enable a program to repeat a block of code multiple times.
• Common iteration statements include for, while, and do-while loops.
• for loops are used when the number of iterations is known.
• while loops repeat a block of code as long as a specified condition remains true.
• do-while loops execute at least once before assessing the condition.

Arrays

• Arrays organize data by holding collections of elements of same type.
• Array elements can be reached using an index.
• Arrays can be one-dimensional, two-dimensional (matrices), or multi-dimensional.
• Arrays allow efficient organization and manipulation of large amounts of data.
• Static arrays have a fixed size set during compilation.
• Dynamic arrays adjust in size during runtime.

Array Operations

• Common array operations include: accessing, inserting, deleting, searching and sorting elements.
• Accessing an element involves using its index to retrieve its value.
• Inserting an element involves adding a new element to the array, which may require shifting.
• Deleting an element involves removing an element from the array, which may require shifting.
• Searching for an element involves finding the index of a specific value in the array
• Sorting elements involves arranging the elements in a specific order

Strings

• Strings consist of a series of characters
• Representing text in programs is done using strings
• In some languages, strings can be treated as character of arrays, whereas others feature a string data type
• A common programming task is string manipulation

String Operations

• Common string operations are concatenation, substring extraction, searching, replacing, comparing andformatting
• Joining strings is concatenation
• Getting a part of a string is substring extraction
• Finding a substrings position is searching
• Replacing one substring with another is replacing
• Comparing strings determines their lexicographical order
• Changing the look of a string is formatting

Functions

• Reusable code blocks performing specific tasks are called functions
• They encapsulate a set of instructions and can be called from anywhere in the program
• Modularity, reusability, and readability are all boosted by functions
• Parameters can be passed into functions and output values can be returned

Function Definition

• A function definition specifies the name, parameters, return type, and body
• Calling the function uses the function name
• Parameters are input values that the function receives
• The return type specifies the data type of the value that the function returns
• The function body contains the instructions that the function executes

Function Call

• Executing a function involves a function call
• The program jumps to the functions definition, executes instructions, then returns to the call point when a function is called
• These values passed to the function are known as arguments during a function call

Function Parameters

• Variables that receive input values when a function is called are called parameters
• Parameters are declared in the function definition as formal parameters
• The values passed to the function when called are actual parameters (arguments)
• Parameters can be passed by value or by reference
• Pass by value: The function receives a copy of the argument's value, thus changes to the parameter do not affect the original argument
• Pass by reference: The function receives a reference to the argument's memory location, thus changes made will affect the original argument

Return Values

• Returning a value to the calling code is done with a return statement
• The result of the function's computation is the return value
• Functions that do not return a value are said to have a void return type

Scope of Variables

• The scope of a variable refers to the region of the program that can access the variable
• Local variables are declared within a function and are only accessible within that function
• Global variables are declared outside any function and can be accessed anywhere in the program
• Using local variables promotes code modularity and reduces the risk of naming conflicts

Recursion

• When a function calls itself, it is called recursion
• A base case is needed so recursive functions can stop and avoid infinite loops
• Breaking down problems into smaller subproblems can be solved with recursion