ICDL Coding Principles (ICDL) cheat sheet

Sequence: statements execute top to bottom in written order unless a control structure alters the flow.

Selection: IF/ELSE and CASE choose a branch by evaluating a Boolean condition; exactly one branch of a two-way IF runs.

Iteration: a count-controlled loop repeats a fixed number of times; a condition-controlled loop repeats while or until a test is true.

A WHILE loop tests before the body (may run zero times); a REPEAT/UNTIL loop tests after the body (runs at least once).

Assignment stores a value in a variable; comparison (equality) tests values and returns a Boolean - do not confuse = with ==.

A variable is a named storage location whose value can change; a constant is assigned once and cannot be reassigned.

Local variables exist only inside the subprogram that declares them; global variables are visible throughout the program.

A function returns a value to the caller; a procedure performs actions without returning a value.

Validation checks input against rules (range, type, presence, length) before it is accepted or processed.

Decomposition: break a large problem into smaller sub-problems that can be solved and tested independently.

Abstraction: remove irrelevant detail and keep only the features needed to solve the problem.

Pattern recognition: identify recurring structures or repeated steps so one reusable solution can serve many cases.

Algorithm: a finite, ordered, unambiguous set of steps that solves a problem and terminates.

Pseudocode is language-independent structured English; a flowchart uses standard symbols - oval for start/end, parallelogram for input/output, rectangle for process, diamond for decision.

Trace tables record each variable's value after each step to verify an algorithm's logic by hand.

Linear search checks elements one by one (works on unsorted data); binary search repeatedly halves a sorted list and is faster for large sorted data.

Test data types: normal (valid, expected), boundary (at the edges of valid ranges), and erroneous (invalid, must be rejected).

A dry run executes an algorithm manually with sample inputs to compare actual output against expected output.