CS 101: Introduction to Programming - Lecture 5

Lecture 5: Introduction to Programming (CS 101)

• Course: Introduction to Programming (CS 101)
• Semester: Spring 2024
• Instructor: Preethi Jyothi
• Lecture materials based on material developed by Prof. Abhiram Ranade

Recap-I (Nested if): Dangling else problem

• Code snippet with nested if statements provided
• Output from the provided code is ambiguous about output/logic due to possible errors in the formatting/nesting of code
• Correct understanding of program output depends on the precise way the statements are grouped in the code

Recap-II (while statement)

• Program's output (in words) for a given input n = 44
• Value of p printed when n = 44 in a while loop program is 32
• #include <simplecpp> statement is standard for simple C++ programs
• Program snippet demonstrates C++ code which takes input n and calculates p iteratively

Recap-III (while and break)

• Demo in class and code (guess.cpp) shared on Moodle

Constants

• Lecture topic is constants

• Course: CS 101, 2025

• Constant definition: constant value doesn't change throughout the program

• const int i = 1; defines integer variable i and initializes with the value 1

• i is a constant in this code

• 1 is a literal in this code

• Constants must be properly initialized and declared

• Using constants over literals improves code readability and maintainability

for statement

• Lecture topic is for statements in CS101, 2025

Motivation: for statement

• Program example: prints a cube table for numbers from 1 to 100
• repeat(100) loop structure can be functionally replaced by a for loop.

for syntax and semantics

• Syntax of a for loop in C++ with initialization, condition, and update statements
• Semantics/logic of for loop: initialization runs before first iteration, condition evaluates repeatedly within iteration, body gets executed when condition is true, update runs after each iteration, loop stops when condition is false.
• Examples of C++ for loop

while and for

• Comparison between while and for loops
• Illustrates how the for loop is used as a concise structure rather than the while loop which can be used instead
• Explains how variables work within loops, and their scopes

for examples

• repeat(n) loop can be replaced with a for loop that is better suited in those scenarios
• for loops are better with certain iterative patterns

Increment, decrement operators

• Explanation of increment (++), and decrement (--) operators in C++
• Pre increment ++i first increments i then uses the incremented value.
• Post increment i++ uses the existing value of i, and then increments i.
• Difference between pre and post increment/decrement operators is important.
• Example code demonstrating how different increment operator varieties are used and what outputs they produce.

Increment, decrement operators (continued)

• Using increment and decrement in a nested loop for example
• Detailed explanation of the differences between pre and post increment and decrement operators using multiple examples to showcase their practical use in C++ coding practices and the specific outputs they will produce.

nested for example

• Example: nested for loops
• Illustrates how nested for loops are created
• Shows how nested loops are functionally and methodologically different

Another for example

• Example of a for loop that handles non-numerical input or a mix of numerical and text input
• Processing character-by-character within a loop

break across different loop structures

• break statement functionality in different types of loops (while, do-while, for) and nested loops

• Breaks the loop structure when executed

continue across different loop structures

• continue statement functionality in different types of loops (while, do-while, for) and nested loops

• Skips rest of the loop structure after being executed

continue in a nested loop

• Example: program with nested for loops and a continue statement
• Illustrates how "continue" impacts the behaviour of nested loops

Next class: Internal Representations of data types

• Topic preview for the next class is internal representations of data types.

This quiz focuses on Lecture 5 from the Introduction to Programming course (CS 101). It covers topics such as nested if statements, while loops, and the use of constants in programming. The aim is to test understanding of the code logic and output related to these programming concepts.