You can initialize an array in the C programming languages in three ways: Not at all, only some elements, or all of the elements. Some compilers offer a fourth way, which initializes all elements to the same value. With the C23 standard, yet another way to initialize an array is possible.
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\nTo review, an array is uninitialized when declared like this:<\/p>\n
The array You can define only a few elements in the array, as I wrote about<\/a> recently:<\/p>\n Above, elements 3 and 4 are set the values 40 and 50, but the other elements remain uninitialized. (This method may be non-standard, implemented only in a few compilers.)<\/p>\n You can define all the elements:<\/p>\n Back in 2020, I wrote about<\/a> initializing all elements in an array to zero:<\/p>\n This construction is non-standard, but it makes you think you can initialize an array to all the same values. Alas, it doesn’t work that way:<\/p>\n The above statement initializes element zero to 1, but the other four elements are set to zero. Again, this construction is compiler-specific and not part of the C standard.<\/p>\n What is part of the new C23 standard, however, is the following expression:<\/p>\n This statement declares an integer array, The code above demonstrates the empty initializer. The expression This code builds under the current version of clang<\/em> without the It’s too bad that C continues to not initialize variables when they’re declared. For example, to set all integers to zero and real numbers to 0.0 as well as pointers to NULL. I don’t know whether such a thing was discussed by the standards committee or even if any negatives are associated. But the addition of the empty initializer as a standard is welcome.<\/p>\n In next week’s Lesson, I review some of the new language features.<\/p>\n","protected":false},"excerpt":{"rendered":" The C23 standard brings consistency when it comes to initializing arrays. Continue reading int values[20];<\/code><\/p>\nvalues[]<\/code> has storage for 20 integers. These storage locations (elements) are defined, but not assigned values. The values could be anything; your code should never assume that all 20 elements are initialized to zero.<\/p>\nint numbers[6] = { [3] = 40, [4] = 50 };<\/code><\/p>\nchar string[] = \"Hello!\";<\/code><\/p>\nint scores[5] = { 0 };<\/code><\/p>\nint scores[5] = { 1 };<\/code><\/p>\nint a[5] = {};<\/code><\/p>\na[]<\/code>, with five elements all initialized to zero. The ={}<\/code> expression is called the empty initializer<\/em>. In fact, it may already be implemented on your compiler, but its standard with C23.<\/p>\n2024_01_13-Lesson.c<\/a><\/h3>\n
\r\n#include <stdio.h>\r\n\r\nint main()\r\n{\r\n int a[5] = {};\r\n\r\n for( int x=0; x<5; x++ )\r\n printf(\"a[%d] = %d\\n\",x,a[x]);\r\n\r\n return 0;\r\n}<\/pre>\nint a[5] = {}<\/code> assigns zeros to the five elements of a[]<\/code>. A for<\/em> loop outputs these values, which are all zeros.<\/p>\n-std=c2x<\/code> switch. Here is the output:<\/p>\na[0] = 0
\na[1] = 0
\na[2] = 0
\na[3] = 0
\na[4] = 0<\/code><\/p>\n