20 min read

Pseudocode Basics

Structured English for planning code: INPUT, OUTPUT, assignment, and how each flowchart symbol becomes a line of pseudocode.

What Is Pseudocode?

"Pseudo" means "not real". Pseudocode is not run by a computer, so small differences in style do not matter — but it must be clear, step by step and structured (with indentation), so that any programmer could turn it into real code.

Some books write assignment as = or SET total TO \dots, and OUTPUT as PRINT or DISPLAY. Any is fine if you are consistent.

Each symbol has a matching line

$Flowchart symbol$	$Pseudocode$
$Terminator: Start / Stop$	$BEGIN / END$
$Parallelogram: INPUT price$	$INPUT price$
$Rectangle: total = price \times quantity$	$total \leftarrow price \times quantity$
$Parallelogram: OUTPUT total$	$OUTPUT total$
$Diamond with Yes/No exits$	$IF \dots THEN \dots ELSE \dots ENDIF$
$Diamond with an arrow back up$	$WHILE \dots ENDWHILE (or FOR / REPEAT)$

Bill with 18% VATPseudocode

1BEGIN2  INPUT price3  INPUT quantity4  total ← price × quantity5  vat ← total × 0.186  total ← total + vat7  OUTPUT "Amount to pay: ", total8END

One instruction per line. Capital letters for keywords (INPUT, IF, WHILE); meaningful names for variables. Indent the lines inside IF, WHILE and FOR blocks. Use \leftarrow (or =) for assignment consistently. Close every block: ENDIF, ENDWHILE, NEXT (or ENDFOR).

Practice

What does total \leftarrow total + price mean?

What Is Pseudocode?

"Pseudo" means "not real". Pseudocode is not run by a computer, so small differences in style do not matter — but it must be clear, step by step and structured (with indentation), so that any programmer could turn it into real code.

Keywords Used in This Course

Some books write assignment as = or SET total TO \dots, and OUTPUT as PRINT or DISPLAY. Any is fine if you are consistent.

From Flowchart to Pseudocode

Each symbol has a matching line

$Flowchart symbol$	$Pseudocode$
$Terminator: Start / Stop$	$BEGIN / END$
$Parallelogram: INPUT price$	$INPUT price$
$Rectangle: total = price \times quantity$	$total \leftarrow price \times quantity$
$Parallelogram: OUTPUT total$	$OUTPUT total$
$Diamond with Yes/No exits$	$IF \dots THEN \dots ELSE \dots ENDIF$
$Diamond with an arrow back up$	$WHILE \dots ENDWHILE (or FOR / REPEAT)$

A Sequence in Pseudocode

Bill with 18% VATPseudocode

1BEGIN2  INPUT price3  INPUT quantity4  total ← price × quantity5  vat ← total × 0.186  total ← total + vat7  OUTPUT "Amount to pay: ", total8END

Writing Good Pseudocode

One instruction per line. Capital letters for keywords (INPUT, IF, WHILE); meaningful names for variables. Indent the lines inside IF, WHILE and FOR blocks. Use \leftarrow (or =) for assignment consistently. Close every block: ENDIF, ENDWHILE, NEXT (or ENDFOR).

Practice

What does total \leftarrow total + price mean?