Check Book

This program implements a checkbook reconciliation tool that calculates a running statement balance by collecting deposit totals and outstanding check amounts. The user inputs a closing statement balance, individual deposits (terminated by 0), and individual checks (terminated by 0, stored in a 200-element array). It then displays summary totals and computes a reconciled balance using the formula (statement balance + deposits) − checks. An optional screen displays all entered check amounts in a columnar layout across up to four columns of 21 rows each, using PRINT AT for precise positioning, with FAST/SLOW mode switching during the check-listing routine for faster screen rendering.

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Program Analysis

Program Structure

The program is divided into several functional phases:

1. Initialization (lines 10–90): All working variables and the 200-element array B are set to zero or their initial values.
2. Data Entry (lines 200–400): The user enters the closing statement balance A, then deposits one by one (accumulated in I, counted in E), then checks one by one into array B (accumulated in K, counted in C).
3. Summary Display (lines 490–590): Prints deposit count/total, check count/total, and the reconciled balance (A+I)-K.
4. Menu / Branching (lines 600–670): Offers three options — list checks (Y), show book balance (B), or quit (N).
5. Check Listing (lines 690–770): Displays checks in a columnar layout using PRINT AT, with paging controlled by FAST/SLOW and a keypress wait.
6. Continuation (lines 1000–1040): After listing completes, waits for a keypress and returns to the menu.

Variable Usage

Variable	Purpose
A	Ending statement balance
B()	Array holding up to 200 individual check amounts
C	Count of checks entered
D	Temporary deposit input variable
E	Count of deposits entered
I	Running sum of deposits
J	Loop upper bound (initially 200, later reused as C)
K	Running sum of checks
L	Line counter within current screen page column
S	Loop index for check display
T	Total checks printed so far
W	Current row for PRINT AT
X	Current column offset for PRINT AT
Z	Set to 0 at line 495 but never used subsequently

Columnar Check Display

The check-listing routine at lines 690–730 arranges checks into four columns of 21 rows each on a single screen. The variable L tracks how many items have been printed in the current set of columns, and W/X track the current row and column offset for PRINT AT. When L reaches 21, 42, or 63, the display advances to the next column (incrementing X by 8 and resetting W to 0). When L reaches 84, a full screen of 84 checks has been printed and the display pauses.

FAST mode is engaged at line 691 before printing begins to speed up screen rendering, and SLOW is restored before each keypress pause at lines 745 and 1005.

Key BASIC Idioms

• Deposits and checks use a sentinel-value loop: input continues until the user enters 0, at which point a conditional GOTO jumps past the loop.
• The menu at lines 630–660 polls INKEY$ in a tight loop, branching on “N”, “B”, or “Y”, and repeating on empty string — a standard keypress-detection pattern.
• PAUSE 300 followed by IF INKEY$<>"" / IF INKEY$="" provides a timed keypress wait at lines 750–770 and 1010–1020.

Bugs and Anomalies

• Line 718 dead code: The condition IF L<>21 OR L<>42 OR L<>63 OR L<>84 is always true (a value cannot simultaneously equal all four), so this line unconditionally executes GOTO 730, making the preceding column-advance code at lines 728–729 unreachable via this path. Column advancement only triggers if control falls through from lines 715–716.
• Variable Z: Initialized at line 495 but never read or modified elsewhere — it is unused.
• Variable J reuse: J is initialized to 200 as the FOR loop bound at line 350, then overwritten with C at line 590 and again at line 692. This is harmless but potentially confusing.
• Line 735 GOTO 700: After NEXT S at line 730 exhausts the loop, line 735 jumps back to PRINT AT at line 700 referencing B(S) where S is now out of range; however line 732 catches the T=C case before this occurs in normal use.
• Book balance option (B): The menu at line 640 branches to line 2000, which does not exist in the listing — this feature appears unimplemented.