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Saloni Goyal
Saloni Goyal

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Flow of Control (if, else, while, for)

Branching and loops are at the heart of most calculations and decisions in your program.

Normally code is executed top to bottom. A number of keywords change this:

  • (For branching)
    • if
    • else
  • (For looping)
    • while
    • for

These keywords work with conditions that are logical expressions that can be true or false

(x > 0)
(y - 2 < b)

Here, parenthesis or round brackets are necessary around conditions in C++.


There are operators to compare two operands -

> >= < <= == !=

==: two equal signs are used for comparison
=: single equal sign in used for assignment
!: means 'not'


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  • condition must always have ()
  • statements will run only if condition is true

Code to compare two numbers

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Garbage In, Garbage Out

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Type rules apply here as well. Giving decimal value confuses the parser and secondNumber is assigned value 0.


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  • an else can only be used right after an if
  • here else statements run if condition is false, i.e. i >= j.


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  • keeps going as long as the condition is true
  • curly braces are optional for single line statements but use them anyway
  • a while loop may not run at all if the condition is never true
  • loop body must change something about the condition, otherwise we may have an infinite loop

Comparing two numbers until user says otherwise

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Garbage In, Garbage Out

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Traditional for loop has three parts separated by semi-colons (not commas) -

  • initialiser (typically also declares the variable)
  • continue condition
  • incrementer

Loop body doesn't have to change anything about the condition if the incrementer does.

Tip: Use a debugger to see which statement in executed.

TO-DO: Write a "Guess the Number" game where you hard code a number into code and then prompt user to guess the number. If the guessed number is lesser/greater than the hard coded number, let the user know. If the user guess correctly, prompt success response and exit.

Code for reference.

Other Flow of Control Keywords

  • switch
  • range based for - used with Collections
  • break - makes a loop stop early
  • continue - makes a loop skip some of its processing
  • do (almost never used)
  • goto (almost never used)

Please leave out comments with anything you don't understand or would like for me to improve upon.

Thanks for reading!

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