Taking Stock

This program is a stock portfolio valuation tool that tracks company names, share counts, and current prices to calculate individual holding values and a total portfolio value. On first use, it collects company names and share quantities, storing them in a string array `N$` and a numeric array `S`, then saves both to tape as separate data files using `SAVE DATA` statements. Subsequent runs load those arrays from tape before prompting the user to enter current share prices from newspaper stock quotations. The program supports hardcopy output via an attached thermal printer (TS2040), printing a formatted portfolio report with a decorative header and dollar-sign separator lines. Two distinct `SAVE` lines at lines 9998–9999 demonstrate a deliberate strategy: one saves with `LINE 9995` to auto-load data arrays before starting, while the other saves with `LINE 1` for general-purpose use.

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Program Analysis

Program Structure

The program is organized into three logical phases:

1. Initialization (lines 1–5): Handles first-use branching, disabling FLASH, setting up uppercase input via POKE 23658,8, and initializing the total accumulator.
2. Main valuation loop (lines 10–89): Iterates over each company, prompts for current share price, computes holding value, accumulates total, and optionally prints a formatted hardcopy report to the TS2040 printer.
3. Summary and save routines (lines 176–9999): Displays and prints the portfolio total with a dated label, followed by first-use setup subroutine at line 8000, and tape save/load management lines at 9990–9999.

Data Persistence Strategy

The program separates persistent data from session data. Company names (N$) and share counts (S) are considered stable and are saved to tape as named data files "STOKNAMDAT" and "SHARNUMDAT" respectively via SAVE DATA at line 8050. Current prices (P) and computed values (V) are treated as ephemeral and are only held in session arrays. This design means the user only needs to re-enter prices on each run, not the full portfolio definition.

First-Use Subroutine

Lines 8000–8060 form the first-use setup subroutine, invoked when the user answers “Y” at line 3. It displays multi-screen instructions about data entry requirements, then collects company names and share counts before saving both arrays. The subroutine correctly uses RETURN at line 8060. Notably, this subroutine defines T, N$, and S internally, so control must not reach the main loop (lines 15–75) without having previously defined these arrays — the flow is safe on first use because the subroutine returns to line 5 which re-inputs T and re-dimensions the arrays.

Load Path at Line 9995

Line 9995 is never reached during normal execution; it exists solely as the auto-run target for the SAVE "STOKVALU" LINE 9995 command at line 9998. When the program is loaded via that save, it executes LOAD DATA for both arrays and then jumps to line 1 to begin normal operation. This is a clean bootstrapping pattern for tape-based data loading.

Array Dimensioning Anomaly

The main program dimensions P(T) and V(T) at line 15, but N$(T,10) and S(T) are dimensioned inside the first-use subroutine at line 8020. On subsequent runs (when the user answers “N” to first use), the program skips the subroutine and loads data via the tape load at line 9995 — but if the user runs the main save (LINE 1) and loads it fresh, the arrays N$ and S are never dimensioned before line 15, which would cause an error. The program depends on the correct save variant being used for reliable operation.

Input Validation

Lines 1 and 80 use a guard pattern: if the user presses ENTER with no input (resulting in an empty string), the program loops back to re-ask the question. This prevents accidental blank responses from being treated as valid answers.

Printer Output Formatting

Lines 85–89 and 180 produce printer output using LPRINT. The report includes a decorative separator of underscores, a spaced-out title “T A K I N G S T O C K”, and tabulated columns using TAB positions 18 and 25. The dollar-sign line ($$$$...) is printed to both screen and printer for the totals section.

Key BASIC Idioms and Techniques

• POKE 23658,8 — forces uppercase input mode, appropriate for a data-entry application.
• POKE 23692,255 at line 10 — disables the scroll prompt (“scroll?”), allowing the listing to print without interruption.
• PAUSE 0 followed by implicit keypress detection — used at lines 8006, 8010, and 176 as an efficient “press any key to continue” idiom.
• INPUT with multiple variables in a single statement (line 176) — e.g., INPUT "...MONTH ";M;" DAY ";D;" YEAR ";Y — uses the Spectrum’s multi-variable INPUT syntax.
• Two SAVE variants at lines 9998 and 9999 with different LINE parameters serve different operational contexts, with inline REM comments explaining their intended use.

Variable Summary

Variable	Type	Purpose
I$	String	First-use Y/N response
T	Numeric	Total number of companies
N$	String array (T×10)	Company names (max 10 chars)
S	Numeric array (T)	Number of shares per company
P	Numeric array (T)	Current price per share
V	Numeric array (T)	Computed value per holding
TOT	Numeric	Total portfolio value
C$	String	Printer copy Y/N response
M, D, Y	Numeric	Month, day, year for report date
N	Numeric	Loop counter