Pseudocode: assignment, fields and while blocks

Pseudocode writes a procedure as structured text. It is easier to edit, compare and discuss than a large picture, while keeping the same logic as a flowchart.

From numbered steps to structured blocks #

You could number every process and use jumps such as “go back to step 2”. The lecture instead introduces while to show repetition directly. Braces { } enclose a block, and indentation makes that block easier to read. Start and End labels can often be omitted because execution begins at the top and finishes after the last statement.

Count = 0
while (Pile1 has cards) {
    Read the top card X
    Move X to Pile2
    Count = Count + 1
}
Report Count

The right side is evaluated before the left is replaced #

Count = Count + 1 is an assignment. If old Count is 5, evaluate 5+1 and store 6 as the new Count. It is not the algebra claim 5=6. The Week 1 arrow notation Count ← Count + 1 expresses the same update more visibly.

Field access identifies part of a record #

X.Mathematics means the Mathematics field of the current scorecard X. X.CardNo identifies that card. Names in the supplied tables are used exactly in dataset examples; field names are case-sensitive when a concrete implementation makes them so.

Sum = 0
while (Pile1 has cards) {
    Read top card X
    Move X to Pile2
    Sum = Sum + X.Mathematics
}
Report Sum

The count and sum procedures share the same loop. Only the state variable and per-card update change. For the supplied scorecards, this sum is 2171.

Assignment versus equality #

In this week’s lecture notation, a single = assigns, while == compares for equality and produces True or False. For example, X.Gender == "F" is a condition; Count = Count + 1 is an update. Pseudocode is a chosen notation, so explain the convention rather than assuming every language uses the same symbols.

Source: Lecture 2.9 — Introduction to pseudocodes. Small teaching datasets and diagrams are prepared for these notes; lecture and tutorial totals are identified explicitly.