Solution

Facilities for Scientific Calculator

Basic: Addition, Subtraction, Multiplication, Division, %,
Scientific: sin/cos/tan, log/ln, $x^y$, $\\sqrt{}$, $n!$, $\\pi$, $e$, brackets, DEG/RAD mode, memory (M+/MR/MC), history, error handling (divide by zero).

DFD Level 0 (Context Diagram)

• External Entity: User
• Process: 0 - Scientific Calculator System
• Data Flows: Input Expression / Key Press → System → Result / Error Display

         Input (keys/expression)
User  ─────────────────────►│ 0. Scientific Calculator │─────────────────────► User (Result/Error)
                            │         System           │

DFD Level 1 (Decomposition)

Processes:

1. 1.0 Accept Input - validate keys/expression
2. 2.0 Parse & Convert - infix to postfix / syntax tree, handle brackets
3. 3.0 Compute - ALU + Scientific engine (trig/log/power)
4. 4.0 Display & Memory - show result, update memory/history

Data Stores:

• D1 Memory Store (M values)
• D2 History Log

User → 1.0 Accept Input → 2.0 Parse → 3.0 Compute → 4.0 Display → User
                 ↕                 ↕           ↕
                D2               D1          D2

Description:

• 1.0 checks valid tokens, prevents illegal sequence.
• 2.0 handles operator precedence, RAD/DEG conversion.
• 3.0 calls math library; on error (div/0, domain) routes to error flow.
• 4.0 formats output, manages M+/MR and history scroll.

This satisfies function-oriented analysis for the calculator simulation program.