Color Bars

This program displays a series of animated color and graphics demonstrations using block graphic characters printed across the full 32×22 character screen. The first section fills the screen row by row with cycling INK colors 1–6, producing horizontal color bars; the second section repeats the effect column by column, pausing at column 16 midway through. Subsequent sections overwrite the screen with progressively simpler block graphics — a partial white pattern, a half-block fill using the ▞ character (code 130), a hash-character fill, and finally a sparse dot pattern — each separated by a PAUSE 0 keypress wait. The program loops indefinitely via GO TO 5, which targets a non-existent line, effectively restarting from line 8. The SAVE command at line 9998 stores the program with auto-run enabled via LINE 0.

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Program Analysis

Program Structure

The program is organized as a sequence of self-contained display sections, each terminated by a PAUSE 0 that waits for a keypress before continuing. A final GO TO 5 at line 1000 restarts the loop from before line 8, creating an infinite demonstration cycle. Lines 9997–9998 are utility lines (a STOP guard and a SAVE statement) that are never reached during normal execution.

Lines	Section	Description
8–60	Horizontal color bars	Fills screen row by row, cycling INK 1–6
109–160	Vertical color bars	Fills screen column by column, pauses at column 16
210–230	White block patch	Prints a 6-row block of mixed █ and space graphics at columns 25–31
310–360	Half-block fill	Fills entire screen with the ▞ (▞) block graphic character
410–460	Hash fill	Fills entire screen with # characters in white ink
510–580	Sparse dot pattern	CLS, then places isolated ▖ characters at corners and two rows
1000	Loop	GO TO 5 (non-existent line, falls through to line 8)

Color Cycling Technique

Both the horizontal (lines 9–60) and vertical (lines 109–160) bar sections use the same cycling idiom: variable k is incremented each iteration, and when it reaches 7 it is reset to 1, thereby cycling through INK colors 1 through 6 and skipping color 0 (black), which would be invisible against the black paper. This is a compact modular-arithmetic replacement using a conditional reset rather than the MOD operator.

Notable Techniques

• AT-based screen painting: Every cell is addressed individually with PRINT INK k;AT i,j;"█" rather than using INK statements or attribute manipulation, giving per-cell color control.
• Mid-loop pause: Line 111 inserts a PAUSE 0 when the column index i reaches 16, splitting the vertical bar sweep into two halves viewable separately without restructuring the loop.
• Block graphics variety: The program demonstrates three distinct block graphic characters — \:: (█, full block), \.' (▞, diagonal half-block), and \: /\. (partial blocks) — showing the range of the 2×2 block graphic set.
• Sparse dot pattern: Lines 540–570 use carefully spaced AT positions and string padding to place ▖ characters at specific screen locations, suggesting a rudimentary border or grid effect rather than a filled pattern.
• PAPER 0 / BORDER 0: Set once at line 8 and never changed, ensuring all subsequent colored ink characters appear on a solid black background throughout the entire demonstration.

Anomalies and Observations

• Line 1000 jumps to line 5, which does not exist; execution falls through to line 8, which is a deliberate idiom for a “soft restart” that avoids re-executing any hypothetical initialization-only lines between 5 and 7.
• Variable k is re-initialized to 1 at line 109 before the vertical bar section, ensuring the color cycle restarts cleanly regardless of where k was left by the horizontal section.
• The white block printed in lines 210–226 at columns 25–31 uses a mix of \:: (full block) and \: /\ characters within a single string, creating an irregular pattern; the exact visual depends on character spacing and is likely decorative rather than functional.
• Line 520 prints a single \:' (▛) character at AT 10,15 — a single cell in the middle of the cleared screen — before the sparse dot pattern is built up in subsequent lines, creating a brief isolated graphic flash.