Lecture on Formatted Output with printf

Overview

• Discussion on printing formatted output using printf.
• Comparison of printf with cout.
• printf originates from C Standard I/O Library (<cstdio>).
• Use of printf in other languages such as Java and C#.

Syntax of printf

• Basic syntax: printf(format string, parameters...).
• Format string contains format specifiers.
• Each format specifier corresponds to a parameter.
• Must include #include <cstdio> when using printf in C++.

Example and Explanation

1. Basic Print

   • printf("What's up\n"); similar to cout << "What's up";
   • Moves cursor to the next line after printing.

2. Using Format Specifiers

   • Example: printf("x: %d, y: %.3f\n", x, y);
     • %d: formats integers.
     • %.3f: formats floating-point numbers with 3 decimal precision.
   • Number of parameters must match the number of specifiers.

Detailed Explanation of Format Specifiers

• %c for characters.
• %d or %i for signed decimal integers.
• %lld for long long integers.
• %x for hexadecimal numbers.
• %f for floating-point or double.
• %s for C-style strings.
• %% to print the percent character.

Alignment and Width

• Default alignment is right.
• Use - for left alignment.
• Can specify width and fill characters.

Advanced Format Specifiers

• %10d: allocates 10 spaces, right-aligned.
• %010d: zero-padded, 10 spaces, right-aligned.
• %-10d: left-aligned.

Printing Floating Point Numbers

• Control precision and width using format specifiers.
• Example: %.2f prints two decimal places.
• Printing in scientific notation with %e.

Printing C++ Strings

• Convert C++ strings to C strings using .c_str().
• Example: printf("%20s", cppString.c_str());
• Use %s for string printing.

Practical Usage Example

• Demonstration of printing a formatted table using printf.
• Example: aligning numbers and strings in a table format.

Conclusion

• printf is a versatile tool for formatted output.
• It's a standard in many programming languages.
• Useful for creating neatly formatted tables in programs.
• Upcoming lab exercise to utilize these concepts.