COBOL中的文件處理

Question

我想編寫一個cobol程序來讀取帶有4個字段（EMPID，NAME，STREAM，GRADE）的文件EMP-GRADE，並顯示在輸出中得分爲'A'的員工的詳細信息。我使用在線Cobol編譯器。

IDENTIFICATION DIVISION. 
PROGRAM-ID. SAMPLE1. 
ENVIRONMENT DIVISION. 
INPUT-OUTPUT SECTION. 
FILE-CONTROL. 
SELECT EMPFILE ASSIGN TO 'input.txt' 
ORGANIZATION IS SEQUENTIAL 
ACCESS MODE IS SEQUENTIAL 
FILE STATUS IS WS-FILE-STATUS. 
SELECT EMPA ASSIGN TO 'util.cobc' 
ORGANIZATION IS SEQUENTIAL 
ACCESS MODE IS SEQUENTIAL. 
DATA DIVISION. 
FILE SECTION. 
FD EMPFILE. 
01 NEWFILE. 
05 FS-EMPID PIC 9(6). 
05 FILLER PIC X(50). 
05 FS-NAME PIC A(10). 
05 FILLER PIC X(50). 
05 FS-STREAM PIC A(10). 
05 FILLER PIC X(50). 
05 FS-GRADE PIC A(1). 
05 FILLER PIC X(50). 
FD EMPA. 
01 OUTFILE. 
05 FS-EMPID-OUT PIC 9(6). 
05 FILLER PIC X(50). 
05 FS-NAME-OUT PIC A(10). 
05 FILLER PIC X(50). 
05 FS-STREAM-OUT PIC A(10). 
05 FILLER PIC X(50). 
05 FS-GRADE-OUT PIC A(1). 
05 FILLER PIC X(50). 
WORKING-STORAGE SECTION. 
01 WS-EOF PIC A(1) VALUE "N". 
01 WS-FILE-STATUS PIC X(2). 
PROCEDURE DIVISION. 
MAIN-PARA. 
OPEN INPUT EMPFILE 
OPEN OUTPUT EMPA 
PERFORM READ-PARA THRU READ-PARA-EXIT 
Perform Until WS-EOF = "Y" 
    IF FS-GRADE='A' 
     MOVE NEWFILE TO OUTFILE 
     WRITE OUTFILE 
     END-WRITE 
     DISPLAY OUTFILE 
    ELSE 
    DISPLAY 'NO A GRADE STUDENT IN THE LIST' 
    END-IF 
    PERFORM READ-PARA THRU READ-PARA-EXIT 
    END-PERFORM 
CLOSE EMPFILE. 
CLOSE EMPA. 
STOP RUN. 
MAIN-PARA-EXIT. 
EXIT. 
READ-PARA. 
READ EMPFILE 
AT END MOVE "Y" TO WS-EOF 
NOT AT END DISPLAY NEWFILE 
END-READ. 
READ-PARA-EXIT. 
EXIT. 

上面的是我更新代碼，然後我在「input.txt中」給輸入和我輸出如下

11111 AISHU JAVA B 
22222 RANJU MAINF A 

NO甲年級學生在列表」

Answer 1

您正在讀取您的整個輸入文件，其中包括

PERFORM READ-PARA THRU READ-PARA-EXIT UNTIL WS-EOF="Y" 

聲明。你必須讀取一條記錄，處理它，讀取下一條記錄，處理它，等等。

OPEN INPUT EMPFILE 
OPEN OUTPUT EMPA 
PERFORM READ-PARA THRU READ-PARA-EXIT 

Perform Until WS-EOF = "Y" 
    IF FS-GRADE='A' 
     MOVE NEWFILE TO OUTFILE 
     WRITE OUTFILE 
     DISPLAY OUTFILE 
    END-IF 
    PERFORM READ-PARA THRU READ-PARA-EXIT 
End-Perform 

CLOSE EMPFILE 
CLOSE EMPA 
STOP RUN. 

根據鍛鍊的實際要求，可能還有其他許多改進，但我認爲這解決了您的直接問題。

請注意兩個單獨的PERFORMs的READ-PARA。第一個有時被稱爲啓動讀取，這是一個有用的技術學習。

Answer 2

試試這個代碼：

PROCEDURE DIVISION. 
MAIN-PARA. 
    OPEN INPUT EMPFILE 
    OPEN OUTPUT EMPA 
    PERFORM READ-PARA THRU READ-PARA-EXIT UNTIL WS-EOF = ‘Y’ 
    CLOSE EMPFILE. 
    CLOSE EMPA. 
    STOP RUN. 
MAIN-PARA-EXIT. 
    EXIT. 
READ-PARA. 
    READ EMPFILE 
     AT END 
      MOVE "Y" TO WS-EOF 
      IF WS-F='M' THEN 
       DISPLAY 'NO A GRADE STUDENT IN THE LIST' 
      END-IF 
     NOT AT END DISPLAY NEWFILE 
      IF FS-GRADE='A' THEN 
       MOVE ‘M’ TO WS-F 
       MOVE NEWFILE TO OUTFILE 
       WRITE OUTFILE 
       END-WRITE 
       DISPLAY OUTFILE 
      ELSE 
       CONTINUE 
      END-IF 
    END-READ. 
READ-PARA-EXIT. 
    EXIT.