NB-076
28 lines
1.0 KiB
Markdown
28 lines
1.0 KiB
Markdown
# 25-subprogram
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## 电信业务场景
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计费子程序。通过CALL语句调用计费计算子程序，传入用量和单价参数，返回计费金额。演示USING参数传递和RETURN-CODE使用。
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## Purpose
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Tests COBOL subprogram calling conventions including CALL with literal names,
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CALL with variable program names, and CALL with IS INITIAL.
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## Architecture
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- **callee.cbl** — Subprogram (PROGRAM-ID. callee) that adds two numbers via
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LINKAGE SECTION parameters and tracks first-call state.
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- **caller.cbl** — Main program (PROGRAM-ID. caller) with three test cases.
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## Tests
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1. **CALL literal**: CALL "callee" USING 100 200 -> expects 300
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2. **CALL variable**: CALL WS-PGM-NAME USING 10 20 -> expects 30
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3. **CALL IS INITIAL**: CALL "callee" IS INITIAL USING 1 2 -> expects 3,
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forces subprogram reinitialization
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## Key Techniques
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- CALL USING for parameter passing
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- LINKAGE SECTION for parameter definitions
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- GOBACK to return to caller
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- RETURN-CODE for status communication
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- IS INITIAL to reinitialize subprogram state
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