Why is using a constant considered a better programming style than using a literal?

Question

Why is using a constant considered a better programming style than using a literal? What is the exact advantage of the previous compared to the last?

Answer 1

One reason is to help with maintenance. Let's say you are stuck in the dark ages, and your graphic manipulation program only works with 1.4 M. floppy disks.

You get a request to work with the new 2.8M flash drives, and you think about yourself: "Ha, I just need to find the code looking for 1440 and replace it with 2880. Simple, huh?"

, , 1440 , , , - . D'Oh!

, 1440 .

:

#define TWIPS_PER_INCH 1440
#define DISK_SZ 1440

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#define SEVENTY_TWO 72

, , , , 72 ( ).

---

- . , , 1.414. SQR_ROOT_OF_2, , . , :

SECS_PER_DAY      86400
CUST_ADDR_LINES   7
INVALID_ID        -1
DAYS_PER_CENTURY  36524
PASS_LEVEL        63
MIN_REPUTATION    10000
MAX_LOAN_AMT      200000

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Answer 2

, .

:

x = 3.14 * 3 ^ 2;

x = PI * RADIUS ^ 2;

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Answer 3

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Answer 4

• , , . , , . , . , , , .
• . , if (m > MONTHS_PER_YEAR), if (m > 12), , m . ( , , MONTHS_PER_YEAR, m "", 12 ).
• PI, ( "" , ).

Answer 5

, , , . , #define SEVENTY_TWO 72, , .

Answer 6

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:

x = y * 100 / 2;

x = y * 50;

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:

x = y * CENTS_IN_DOLLAR / NO_OF_PARKING_METERS;

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