{"id":7217,"date":"2025-11-01T00:01:24","date_gmt":"2025-11-01T07:01:24","guid":{"rendered":"https:\/\/c-for-dummies.com\/blog\/?p=7217"},"modified":"2025-11-08T10:00:26","modified_gmt":"2025-11-08T18:00:26","slug":"having-fun-with-goto","status":"publish","type":"post","link":"https:\/\/c-for-dummies.com\/blog\/?p=7217","title":{"rendered":"Having Fun with goto<\/em>"},"content":{"rendered":"

Difficulty: ★ ★ ★ ☆<\/h2>\n

Among the C language’s slender assortment of keywords you find goto<\/em>. It’s a branching statement, which can be used to loop or to escape from some ugly programming knot. Regardless, you’re told early on in your C language education that you must avoid this keyword at all costs! That is, unless you want to try this month’s exercise.
\n
\nAs a review, the goto<\/em> keyword branches program execution to a label. Labels are things you probably don’t use often in C programming, though they do appear inside a switch-case<\/em> structure. The label is the only thing on a line of text. It’s an identifier (named like a variable) immediately followed by a colon:<\/p>\n

there:<\/code><\/p>\n

This label serves as a target for the goto<\/em> statement:<\/p>\n

goto there;<\/code><\/p>\n

The goto<\/em> statement ends with a semicolon, which is something you might forget (or use a colon instead). After encountering the above statement, program flow jumps to the there<\/code> label and continues execution. It’s this aspect of goto<\/em> that requires the warning: Using goto<\/em> to hippity-hop around your source code makes the code difficult to read and lends itself to other unnecessary problems. The descriptive term is “spaghetti code,” which isn’t flattering. Even so, goto<\/em> is a valid keyword and has never been deprecated.<\/p>\n

Consider the following code, which demonstrates a nested loop:<\/p>\n

2025_11_01-Exercise.c<\/a><\/h3>\n
\r\n#include <stdio.h>\r\n\r\nint main()\r\n{\r\n    int a;\r\n    char b;\r\n\r\n    for( a=0; a<10; a++ )\r\n    {\r\n        for( b='A'; b<'K'; b++ )\r\n        {\r\n            printf(\"%c%d  \",b,a);\r\n        }\r\n        putchar('\\n');\r\n    }\r\n\r\n    return 0;\r\n}<\/pre>\n
Like most nested loops I can think of, this one processes a matrix, rows of numbers and letters, all neatly presented in a grid:<\/p>\n
A0  B0  C0  D0  E0  F0  G0  H0  I0  J0  
\nA1  B1  C1  D1  E1  F1  G1  H1  I1  J1  
\nA2  B2  C2  D2  E2  F2  G2  H2  I2  J2  
\nA3  B3  C3  D3  E3  F3  G3  H3  I3  J3  
\nA4  B4  C4  D4  E4  F4  G4  H4  I4  J4  
\nA5  B5  C5  D5  E5  F5  G5  H5  I5  J5  
\nA6  B6  C6  D6  E6  F6  G6  H6  I6  J6  
\nA7  B7  C7  D7  E7  F7  G7  H7  I7  J7  
\nA8  B8  C8  D8  E8  F8  G8  H8  I8  J8  
\nA9  B9  C9  D9  E9  F9  G9  H9  I9  J9  <\/code><\/p>\n
Your task for this month’s Exercise is to generate identical output by using goto<\/em> statements and labels instead of nested for<\/em> loops.<\/p>\n
The difficulty level for this challenge to three out of four stars, which isn’t because the program itself is tough to code. No, the problem is that your C programming brain isn’t trained to think of goto<\/em> as a way to accomplish this task. Yes, even though the solution presents as C code, it’s not an approach any C programmer would ever consider!<\/p>\n
Have fun with this one! I know that I did. I marveled at my solution<\/a>, not because it was anything that would win an award, but that it was entirely possible using a weirdo approach to C coding that I’ve never considered.<\/p>\n","protected":false},"excerpt":{"rendered":"
It’s the keyword you should avoid — except for in this challenge! Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-7217","post","type-post","status-publish","format-standard","hentry","category-exercise"],"_links":{"self":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/7217","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=7217"}],"version-history":[{"count":5,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/7217\/revisions"}],"predecessor-version":[{"id":7246,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/7217\/revisions\/7246"}],"wp:attachment":[{"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=7217"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=7217"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c-for-dummies.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=7217"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}