Library Routines & Operators
1. The Three Categories of Operators
A. Arithmetic Operators
These are used to perform mathematical calculations on numerical data types (Integer and Real).
| Operator | Function | Example |
|---|---|---|
| + | Addition | 10 + 5 = 15 |
| - | Subtraction | 10 - 5 = 5 |
| * | Multiplication | 10 * 5 = 50 |
| / | Division | 10 / 4 = 2.5 |
| DIV | Integer Division (Quotient only) | 10 DIV 4 = 2 |
| MOD | Modulo (Remainder only) | 10 MOD 4 = 2 |
B. Relational (Comparison) Operators
These compare two values and return a Boolean result (TRUE or FALSE). Used in IF statements and Loops.
| Operator | Function | Example |
|---|---|---|
| = | Equal to | X = 10 |
| <> | Not equal to | X <> 10 |
| > | Greater than | X > 10 |
| < | Less than | X < 10 |
| >= | Greater than or equal to | X >= 10 |
| <= | Less than or equal to | X <= 10 |
C. Boolean (Logical) Operators
Used to combine multiple conditions together to form complex logic.
| Operator | Function | Example |
|---|---|---|
| AND | True only if BOTH are true | (X > 5) AND (X < 10) |
| OR | True if AT LEAST ONE is true | (Ans = 'Y') OR (Ans = 'y') |
| NOT | Reverses the Boolean value | NOT (X = 10) |
2. Official Library Routines (String Handling)
The following are the only string functions recognized in the Cambridge marking schemes:
| Routine | Function |
|---|---|
| LENGTH(String) | Returns the length of the string as an integer. |
| LCASE(String) | Converts all characters to lowercase. |
| UCASE(String) | Converts all characters to uppercase. |
| SUBSTRING(s, start, length) | Extracts a portion of string s starting at start for length. |
| LEFT(String, n) | Returns the first n characters of the string. |
| RIGHT(String, n) | Returns the last n characters of the string. |
// Example usage in an algorithm
DECLARE MyText : STRING
MyText ← "Cambridge"
OUTPUT LENGTH(MyText) // Result: 9
OUTPUT SUBSTRING(MyText, 1, 3) // Result: "Cam"
3. Numeric & Random Routines
| Routine | Function |
|---|---|
| INT(n) | Returns the integer part of value n. |
| ROUND(n, d) | Rounds n to d decimal places. |
| RANDOM() | Returns a random real number between 0 and 1 inclusive. |
📝 Exam Note (Very Important):
In Cambridge pseudocode, the Assignment Operator is an arrow: ←.
Using a single equals sign (=) for assignment is a common mistake; it should only be used for comparison.