Volumes: Geometry

This program calculates the volumes of six geometric shapes: cone, pyramid, prism, cube, cylinder, and sphere. The user selects a shape by typing its name, then enters the required dimensions such as area, height, radius, length, or width. Volumes are computed using standard mathematical formulas, including the built-in PI constant and the exponentiation operator (**) for the sphere formula V = (4·π·r³)/3. After displaying the result, the program waits for a keypress using a busy-loop on INKEY$ before clearing the screen and looping back for another calculation.

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Program Analysis

Program Structure

The program is organized into clearly separated blocks by line-number range:

Line range	Purpose
1–30	Title display and initialisation
100–170	Shape selection menu and input dispatch
200–280	Cone / Pyramid / Prism handler (area × height)
300–350	Cube/cuboid handler (length × width × height)
400–470	Cylinder handler (2·π·r·h)
500–530	Sphere handler (4·π·r³/3)
600–660	Result display, keypress wait, loop back
700–800	SAVE and RUN utility lines

Input and Dispatch

Shape selection is handled by a cascade of IF … THEN GOTO statements at lines 130–160. If none of the recognised strings matches X$, line 170 loops back to 100, effectively re-prompting without an explicit error message. The cone, pyramid, and prism cases are grouped at line 130 because they all share the same base formula (area × height), with the cone and pyramid then halved further at line 270.

Volume Formulas

Shape	Formula used	Notes
Prism	V = A × H	Correct
Cone / Pyramid	V = A × H / 3	Correct (1/3 base × height)
Cube / Cuboid	V = L × W × H	Correct
Cylinder	V = 2·π·R·H	Bug: should be π·R²·H; missing R factor, multiplies by 2 instead
Sphere	V = (4·π·R³) / 3	Correct

Notable Techniques

• The built-in PI constant is used directly in lines 460 and 530, avoiding the need for a numeric approximation.
• The exponentiation operator ** is used in line 530 (R**3) for the sphere formula, which is the standard power operator in this BASIC dialect.
• The cone/pyramid shortcut at lines 260–270 computes V = A*H first and then conditionally divides by 3, sharing code with the prism case neatly.
• A busy-loop keypress wait at line 640 (IF INKEY$="" THEN GOTO 640) pauses until any key is pressed before clearing the screen and recycling.
• Line numbering uses deliberate gaps (e.g. 300, 305, 310 …) in the cube block, suggesting the section was added or expanded after the initial numbering scheme was laid out.

Bugs and Anomalies

The cylinder volume formula at line 460 is incorrect. It reads LET V=2*PI*R*H, which equals 2πrh (the lateral surface area of a cylinder, not its volume). The correct formula is V = π·R²·H, which would be written LET V=PI*R*R*H or LET V=PI*(R**2)*H.

The label in the shape prompt at line 100 says “CUBE” but the handler at lines 300–345 accepts three independent dimensions (length, width, height), making it a general cuboid calculator rather than a cube-only one. No validation ensures L = W = H for a true cube.