This Lesson’s topic is more about database programming than C programming, but the philosophy still applies. When do you store a number as a value as opposed to storing it as a string? Two famous examples are zip codes and phone numbers.
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\nI suppose the answer depends on what you plan on doing with the number. For example, if a zip code needs to be part of a mathematical expression, assigning it as a value makes sense. Sorting, of course, works with both strings and values. When storage is an issue, values occupy less space than strings.<\/p>\n
For practice, assume the task is to format a phone number. The point isn’t to sort the number or to process it through the phone system, but just to present what starts as a value as a formatted string. Specifically, take the long int<\/em> value I can think of two ways to accomplish this task in C. The first and easiest is to convert the long int<\/em> value into a string. The string is then output one character at a time, interspliced with the proper phone number formatting characters as presented in the United States. Here is the string conversion code:<\/p>\n The snprintf()<\/em> function converts the long int<\/em> value stored in variable Constant integer A for<\/em> loop outputs characters in Here is the output:<\/p>\n The string approach is easy because strings are naturally processed from left-to-right. I don’t know whether this simplicity of processing means that it’s best to store a phone number as a string. Such a decision is still up to whomever is coding the database, but it’s certain uncomplicated from my perspective.<\/p>\n What’s more difficult is processing output when the phone number is stored as a value. This task requires some additional thinking plus a sprinkling of math, but it still works sorta the same. I present a solution in next week’s Lesson<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":" Sometimes numeric data shouldn’t be stored numerically. Continue reading 5551234001 <\/code>and output it as the string (555) 123-4001<\/code>.<\/p>\n2025_03_29-Lesson.c<\/a><\/h3>\n
\r\n#include <stdio.h>\r\n\r\nint main()\r\n{\r\n \/* phone numbers for this example have 10 digits *\/<\/span>\r\n const int digits = 10;\r\n const int open_paren = 0;\r\n const int close_paren = 3;\r\n const int dash = 6;\r\n long phone;\r\n char number[digits+1];\r\n int x;\r\n\r\n \/* assign phone number as long value *\/<\/span>\r\n phone = 5551234001;\r\n\r\n \/* convert to a string *\/<\/span>\r\n snprintf(number,digits+1,\"%ld\",phone);\r\n\r\n \/* process the phone number *\/<\/span>\r\n for( x=0; x<digits; x++ )\r\n {\r\n switch(x)\r\n {\r\n case open_paren:\r\n printf(\"(%c\",number[x]);\r\n break;\r\n case close_paren:\r\n printf(\") %c\",number[x]);\r\n break;\r\n case dash:\r\n printf(\"-%c\",number[x]);\r\n break;\r\n default:\r\n printf(\"%c\",number[x]);\r\n }\r\n }\r\n putchar('\\n');\r\n\r\n return 0;\r\n}<\/pre>\nphone<\/code> to a string, stored in char<\/em> array buffer[]<\/code>:<\/p>\nsnprintf(number,digits+1,\"%ld\",phone);<\/code><\/p>\ndigits<\/code> stores the phone number’s length, 10 characters. But to assign storage for the string, one extra byte is required for the null character: char number[digits+1]<\/code> This value is also used in the snprintf()<\/em> statement to ensure that the entire string fits in buffer[]<\/code>, digits+1<\/code>. (When you forget to add one, the output is truncated.)<\/p>\nbuffer[]<\/code> one at a time. A switch-case<\/em> structure monitors the offsets, outputting formatting characters at their proper locations in the string. These positions are set by using constants: open_paren<\/code>, close_paren<\/code>, and dash<\/code>.<\/p>\n(555) 123-4001<\/code><\/p>\n