# Common Operations & Built-in Functions

> Cambridge Assessment International Education (CAIE) Pseudocode Reference Guide
> Applicable Syllabus: **IGCSE & A Level**

Cambridge pseudocode I/O routines, arithmetic (DIV/MOD), relational operators, Boolean logic, and unified string & numeric built-in functions.

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Standard input/output commands, arithmetic operators, relational and Boolean logic, and unified string & numeric built-in functions.

### 5.1 Input & Output

```pseudocode
// runnable
// Input and output demo
DECLARE Answer, Score, Lives : INTEGER
Score <- 10
Lives <- 3
INPUT Answer
OUTPUT "Your answer: ", Answer
OUTPUT Score
OUTPUT "You have ", Lives, " lives left"
```

### 5.2 Arithmetic Operators

| Operator | Description |
|----------|-------------|
| `+` | Addition |
| `-` | Subtraction |
| `*` | Multiplication |
| `/` | Division (result is always REAL) |
| `DIV` | Integer division (quotient only) |
| `MOD` | Modulus (remainder after division) |

### 5.3 Relational Operators

| Operator | Description |
|----------|-------------|
| `>` | Greater than |
| `<` | Less than |
| `>=` | Greater than or equal to |
| `<=` | Less than or equal to |
| `=` | Equal to |
| `<>` | Not equal to |

The result of relational operations is always of data type `BOOLEAN`.

### 5.4 Logic Operators

The logic operators are `AND`, `OR`, and `NOT`. Operands and results are always `BOOLEAN`. Use parentheses to make order of operations explicit.

### 5.5 String Functions & Operations

| Function Signature | Description | Example | Syllabus |
|--------------------|-------------|---------|----------|
| `LENGTH(s : STRING) RETURNS INTEGER` | Returns string length | `LENGTH("Happy Days")` -> `10` | Both |
| `MID(s : STRING, x : INTEGER, y : INTEGER) RETURNS STRING` | Returns y chars from position x | `MID("ABCDEFGH", 2, 3)` -> `"BCD"` | 9618 |
| `RIGHT(s : STRING, x : INTEGER) RETURNS STRING` | Returns rightmost x chars | `RIGHT("ABCDEFGH", 3)` -> `"FGH"` | 9618 |
| `LEFT(s : STRING, x : INTEGER) RETURNS STRING` | Returns leftmost x chars | `LEFT("CAMBRIDGE", 3)` -> `"CAM"` | 0478 |
| `SUBSTRING(s : STRING, x : INTEGER, y : INTEGER) RETURNS STRING` | Extracts y chars from position x | `SUBSTRING("HELLO", 2, 3)` -> `"ELL"` | 0478 |
| `LCASE(c : CHAR) RETURNS CHAR` | Returns lower-case equivalent | `LCASE('W')` -> `'w'` | Both |
| `UCASE(c : CHAR) RETURNS CHAR` | Returns upper-case equivalent | `UCASE('h')` -> `'H'` | Both |
| `&` (concatenation) | Joins two strings | `"Summer" & " Pudding"` -> `"Summer Pudding"` | Both |

### 5.6 Numeric Functions

| Function Signature | Description | Example | Syllabus |
|--------------------|-------------|---------|----------|
| `INT(x : REAL) RETURNS INTEGER` | Returns integer part of x | `INT(27.5415)` -> `27` | Both |
| `RAND(x : INTEGER) RETURNS REAL` | Random real in range 0 to x (exclusive) | `RAND(87)` may return `35.43` | 9618 |
| `NUM_TO_STR(x) RETURNS STRING` | Converts number to string | `NUM_TO_STR(42)` -> `"42"` | 0478 |
| `STR_TO_NUM(s : STRING) RETURNS NUMERIC` | Parses string to number | `STR_TO_NUM("42")` -> `42` | 0478 |
| `ROUND(x : REAL, places : INTEGER) RETURNS REAL` | Rounds to the given number of decimal places | `ROUND(7.246, 2)` -> `7.25` | 0478 |
| `RANDOM() RETURNS REAL` | Random real between 0 and 1 | `RANDOM()` may return `0.64` | 0478 |


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