Lecture on Using scanf in C Programming

Introduction

• Purpose: Understand how to allow user inputs in C programs using the scanf statement.
• Context: Writing code that allows users (who may not know how to code) to input data like numbers.
• Goal: Enable users to input numbers into a C program without recompiling the code.

Setup

• Opening Command Prompt:
  • Open command prompt via cmd.
  • Navigate to directories using cd desktop and cd c\code.
• Running the Program:
  • Use batch file: make project.bat average_width_scanf
  • Open the C file average_with_scanf.c in Notepad++.
• Template: Use average_v2c from previous work.
  • Copy (Ctrl+A, Ctrl+C) and paste (Ctrl+V) the code into the new file.

Code Modifications

• Changing Program Content:
  • Modify the program to take 3 numbers instead of 5.
  • Remove hard-coded assignments (e.g., a[0] = 3, a[1] = 5, a[2] = 8).
• Implementing scanf Loop:
  • Use a for loop to input numbers.
  • scanf Syntax:
    • %f: Expecting a float.
    • %d: Expecting an integer.
    • %g: Float that handles both regular and exponential notation.
    • Include & before variable names in scanf (e.g., &a[i]).

Prompting User

• Initial Setup: Program waits at scanf for user input.
• Improving User Interaction:
  • Add printf before scanf to prompt users.
  • Avoid technical terms (e.g., index numbers) in user prompts.
  • Example: Use a counter variable j (i+1) to display user-friendly prompts.

Compiling and Running the Program

• Compilation:
  • gcc average_with_scanf.c -o average_with_scanf
• Execution: Run program and input numbers when prompted.
• Output: Program calculates the average of the input numbers.

Conclusion

• Usefulness: scanf is less common now for terminal input.
• Next Steps: More common practice is file input; will cover scanning from files in subsequent lessons.