[Adult Learning Log] C Language – Week 4 Review

○ Key Learning Points from Week 4

• Learned about the concepts and types of arithmetic operators, relational operators, logical operators, and conditional operators.
• Studied increment/decrement operators, compound assignment operators, comma operators, and bitwise operators.
• Understood type conversion and operator precedence.

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○ Expression (Formula)

An expression is a combination of constants, variables, and operators, divided into operators and operands.

○ Arithmetic Operators (Basic Arithmetic): +, -, *, /, %

• Division between int types results in an int (decimal parts are truncated).
• Division between float types yields float results.
• % (Modulus Operator) returns the remainder of dividing the first operand by the second operand.

○ Increment/Decrement Operators

• ++variable, variable++, --variable, variable--
• The position of the increment/decrement operator affects when the value is updated.

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○ Assignment Operators

Operators that assign the result of an expression to a variable.

• The left side must be a variable, while the right side can be any expression.

100 = x + y; // Error
x = x + 1;   // Valid (Different from the math "="!)
y = x = 3;   // Valid (Assigns 3 to x, then assigns x's value to y)

○ Compound Assignment Operators

Combines = with arithmetic operators, e.g., x += y.

• Allows shorthand for reassigning the result to the same variable.

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○ Relational Operators: ==, !=, >, <, >=, <=

• Compares two operands; returns TRUE (1) or FALSE (0).
• Cannot chain comparisons as in math: 2 < x < 5 → This is invalid.
  • Correct way: (2 < x) && (x < 5)

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○ Logical Operators: &&, ||, !

• Used to combine multiple conditions.
• Returns 1 (TRUE) if the condition is met, 0 (FALSE) otherwise.
• In C, non-zero values are considered TRUE and 0 is FALSE.
• Note: In this class, negative numbers were also treated as FALSE due to representing no electric signal.

○ Ternary Operator (Conditional Operator)

• The only operator that takes three operands:

max_value = (x > y) ? a : b;  // Returns a if TRUE, b if FALSE

○ Comma Operator

• Evaluates two expressions separated by , sequentially.

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○ Bitwise Operators: &, |, ^, <<, >>, ~

• << shifts bits to the left, effectively doubling the value per shift (due to binary nature).

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○ Type Conversion & Operator Precedence

Type Conversion (Casting)

• Changes the data type during program execution.
• Be cautious—improper casting can lead to data loss.
• When mixing different data types, C automatically promotes to the larger type.

Explicit Casting

• Developer explicitly converts the type using parentheses before the variable:

(int)1.35  // Casts 1.35 to int

Operator Precedence

• Determines the order of operations among multiple operators.
• Refer to the textbook’s precedence chart for details.

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○ Practice

Try writing and executing C code using the operators learned this week.