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← C Programming for Beginners
○What a program actually does○The computer and the operating system○From a C file to a running program○Compiled and interpreted programs○Demo: Trace One Tiny C Program○Exercise: Print the Opening Sign✦Module Quiz
○Your First C Program○Variables and Formatted Output○Arithmetic and Integer Division○Demo: Formatting and Numeric Conversion○Exercise: Calculate a Shop Total✦Module Quiz
○Demo: Declare and initialize variables○Exercise: Declare and initialize variables○Demo: Assign a new value○Exercise: Assign a new value○Demo: Choose int, double, and char○Exercise: Choose int, double, and char○Demo: Keep local names and constants clear○Exercise: Keep local names and constants clear✦Module Quiz
○Demo: Match printf placeholders and arguments○Exercise: Match printf placeholders and arguments○Demo: Build lines with escapes and multiple calls○Exercise: Build lines with escapes and multiple calls○Demo: Print percent signs and aligned values○Exercise: Print percent signs and aligned values○Demo: Evaluate expressions before printing○Exercise: Evaluate expressions before printing✦Module Quiz
○Comparisons and True or False○How if and else Choose a Path○Exercise: Choose a Ticket Message○Demo: Select a Fixed Choice with switch○Exercise: Choose a Service Desk✦Module Quiz
○For Loops: Repeat a Known Number of Times○Exercise: Add Daily Contributions○While Loops: Repeat While a Condition Holds○Exercise: Make a Countdown○Demo: Run Once with do while○Demo: Label a Two-Row Shelf○Exercise: Label Tool Drawers✦Module Quiz
○Define and Call a Function○Follow a Function Call and Its Return Value○Exercise: Return a Square○Demo: Declare Before a Function Call○Exercise: Declare and Convert✦Module Quiz
○Arrays and Zero-Based Indexes○Exercise: Add Array Elements○Demo: Count Array Slots Safely○Exercise: Average Workshop Ratings○Demo: Rows and Columns in Memory○Exercise: Total a Two-Row Grid✦Module Quiz
○C Strings and the Null Terminator○Exercise: Count a Label○Demo: Compare Complete Strings○Exercise: Verify a Pickup Code○Demo: Visit Each Character○Exercise: Count a Letter in a Label✦Module Quiz
○Pointers: Addresses and Dereferencing○Exercise: Update Through a Pointer○Demo: Pass an Address to a Function○Exercise: Swap Two Counts○Demo: Array Addresses and Offsets○Exercise: Total with an In-Bounds Pointer○Demo: Null, Validity, and Lifetime○Exercise: Handle an Optional Pointer✦Module Quiz
○Demo: Pass an Array and Its Length○Exercise: Total Readings in a Function○Demo: Change Array Elements Through a Parameter○Exercise: Update Each Stock Count✦Module Quiz
○Define a Supply Record○Exercise: Define a Supply Record○Update a Record Member○Exercise: Update a Record Member○Walk an Array of Records○Exercise: Walk an Array of Records○Pass a Record to a Function○Exercise: Pass a Record to a Function✦Module Quiz
○Demo: One Value in Shared Storage○Exercise: Record One Ticket Value○Demo: A Tag Tells You What Is Stored○Exercise: Read a Tagged Repair Ticket○Demo: Compare Union and Struct Storage○Exercise: Choose the Right Storage✦Module Quiz
○Demo: Read Bits with AND○Exercise: Check an Equipment Flag○Demo: Turn a Flag On with OR○Exercise: Mark a Kit Ready●Demo: Toggle and Clear Individual Flags○Exercise: Toggle a Warning Flag○Demo: Move a Bit into Position○Exercise: Build a Position Mask✦Module Quiz
○Include the Right Header○Exercise: Include the Right Header○Guard a Macro Default○Exercise: Guard a Macro Default○Demo: Include Code Only for Debug Builds○Exercise: Gate an Inventory Diagnostic○Demo: Parenthesize a Simple Macro○Exercise: Keep a Macro Calculation Grouped✦Module Quiz
○Name a Status with enum○Exercise: Name a Status with enum○Alias a Record Type with typedef○Exercise: Alias a Record Type with typedef✦Module Quiz
○Where the storage comes from○Demo: Request and Release an Array○Exercise: Store Three Repair Counts○Demo: Start Allocated Counters at Zero○Exercise: Start Station Counters at Zero○Allocate and Release Records○Exercise: Allocate and Release Records✦Module Quiz
○Print a Formatted Label○Exercise: Print a Formatted Label○Print Characters with putchar○Exercise: Print Characters with putchar○Format into a Bounded Buffer○Exercise: Format into a Bounded Buffer○Write a Line to stdout with fputs○Exercise: Write a Line to stdout with fputs○Input and Diagnostics in a Local Terminal✦Module Quiz

Demo: Toggle and Clear Individual Flags

Toggle or clear one flag

XOR (^) flips a selected bit: on becomes off, and off becomes on. If you need the bit off regardless of its starting state, use flags & ~mask instead. ~ complements every bit of the unsigned mask; the following AND clears the selected bit while preserving the others. Logical ! is different: it produces a truth value.

c
#include <stdio.h>

int main(void) {
    unsigned int flags = 0x5u; /* 0101 */
    unsigned int target = 0x4u; /* 0100 */
    flags ^= target;           /* 0001 */
    printf("Toggled: %u\n", flags);
    flags |= target;           /* 0101 again */
    flags &= ~target;          /* 0001 */
    printf("Cleared: %u\n", flags);
    return 0;
}

Trace the low four bits through each assignment. Toggling a bit twice returns it to where it started; clearing twice still leaves it off. For the exercise, you'll toggle.