Understanding Loops in Programming

• The document covers loops, arrays, and functions in C++ programming

Loops

• Loops allow repetitive execution of a statement or block of statements
• Loops save programming time and effort, especially for tasks needing many repetitions

Elements of Looping

• A loop requires specific key elements to work properly
• Missing any of these elements will cause errors

Loop Control Variable (LCV)

• The loop control variable holds the value that is is compared to a limit
• The limit determines when the loop ends
• The loop control variable must be initialized before use in the program

Sentinel Value (SV)

• The sentinel value is the limit to which the loop control variable is compared
• Boolean values of true or false determine whether the loop continues or stops operation, based on the result of the comparison

Loop Update (LU)

• Inside the loop, the value of the loop control variable must be altered
• Called the loop update, it changes value through incrementing or decrementing
• The increment operator (++) adds 1 to its operand
• The decrement operator (--) subtracts 1 from its operand.
• 'x++' is equivalent to 'x = x + 1'
• 'x--' is equivalent to 'x = x - 1'
• Increment/decrement operators can be prefix (++x) or postfix (x++)
• Prefix form does increment/decrement before evaluating the expression, while postfix does the opposite
• Increment and decrement can add or subtract any (appropriate) value from the loop control variable

Infinite and Empty Loops

• An infinite loop is a loop that never stops because there is no end condition
• A loop is called empty when the comparison expression evaluates to false on the first try

Types of Loops

• There are several types of loops in C++

For Loop

• Is a repetition control structure
• Is used to efficiently create a loop that executes for a specific number of times
• Syntax: for (initialization; comparison expression; update) { statement(s); }
• The initialization of the loop control variable is executed once
• The comparison expression is evaluated next
• If the comparison is true, the loop body executes, otherwise the loop does not execute
• After the body is executed, the flow jumps to the update statement
• The update statement can increment or decrement the loop control variable

While Loop

• Another loop form
• Repetitive tasks assigned to it are like in a *for *loop
• Initialization of the loop control variable is typed before the structure of the loop
• Loop update placed inside the loop body.
• Syntax:

  initialization;
  while (comparison expression)
  {
         statement/s;
         loop update;
  }
  

Do While Loop

• Functions like a for or while loop
• Comparison happens at the end; the body executes at least once
• Syntax:

initialization;
do
{
  statement/s;
  loop update;
} while (comparison expression);

Nested Loops

• A loop within a loop
• Contains an outer loop and an inner loop.
• The outer loop is executed first.
• When the outer loop's comparison evaluates to true, its body executes
• The inner loop executes, and when its comparison evaluates to true, the inner loop's body executes repeatedly until the comparison is false
• Then, the inner loop terminates
• Statements inside the outer loop's body (after the inner loop) execute
• The outer loop updates, and the process repeats until the overall termination
• The total number of executions of a nested loop, is equal to the number of iterations of outer loop times the number of iterations of the inner loop

Arrays

• Is a series of elements with the same data type
• Elements are placed in adjoining memory locations
• Each element can be referenced individually by adding an index to the array's identifier
• Syntax: data_type array_name[no_of_elements];
  • data_type is any valid data type (int, float, etc.)
  • array_name is a valid identifier
  • no_of_elements is the length of the array
• Arrays are blocks of static memory
• Array size must be determined when the program is compiled
• The first element is always at index [0]
• The indexes increase, e.g. [1], [2], and so on

Initializing Arrays

• Arrays are not initialized by default
• Arrays are given values declared in opening and closing braces
• Syntax: dataType arrayName[no_of_elements] = {val1, val2,..., valn};
• The number of values inside the braces must not be greater than the length of the array
• If the number of values is less, the remaining elements will have the default value of 0
• Brackets of the array can be empty, meaning that the length of the array is not specified in the declaration
• If brackets are absent, the compiler will assume the number of values in the array as its length

Array Values

• Assigning a value to an array element is like assigning the value to a regular variable
• Syntax: array_name[index_no];
• It is syntactically correct to exceed the valid range of indices for an array in C++
• Error messages wont necessarily occur
• Problems will be on final output, or during runtime only

Multidimensional Arrays

• An array of arrays
• Common example is the bi-dimensional array
• Can be imagined as a two-dimensional table
• elements have the same data types
• Syntax for declaration: int deron[3][5];
• Multidimensional arrays are not limited to two indices (i.e., two dimensions) and can contain as many indices are needed

Functions

• Modules or segments of code performing individual tasks.
• Is a group of statements given a name
• The function can then be called at some point from the main program
• Syntax: data_type function_name ( parameter_1, ..., parameter_n) { statement_1; statement_2; ... statement_n; }
  • The data_type is the type of data that will be returned by the function
  • The function_name is the identifier by which the function can be called
  • The parameters can be as many as needed
  • Each parameter has a data type and an identifier
• The statements surrounded by braces specify what the function does

Void Functions

• Void functions do not return a value, but only prints messages to the screen
• Created and used just like value-returning functions
• Do not return a value after the function executes
• Instead of a data type, use the keyword "void."

Function Overloading

• A feature of object-oriented programming
• Two or more functions can have the same name but different parameters
  • Number of parameters are is different
  • Based on their position, the type of parameters passed may also be different
• Overloaded functions may or may not have different return types but they must have different arguments

Test your knowledge of loops, increment and decrement opperators, and conditional statements in programming. Loops are essential for repetitive tasks. Identify the key aspects of loop control and execution.