While printing "Hello world", if this error 'Hello' undeclared occurred that means Hello is supplied to the compiler as a variable not as a text/string.

在打印“ Hello world”时 ，如果发生未声明的错误“ Hello” ，则意味着Hello是作为变量而不是text / string提供给编译器的 。

This is possible only, when starting double quote is missing inside the printf(). To fix this error, you should take care of double quotes; place the constant string/text in double quotes.

仅当在printf()中缺少双引号时这才可能。 要解决此错误，您应该注意双引号。 将常量字符串/文本放在双引号中。

Example:

例：

#include <stdio.h>
int main(void) {//closing double quote is missing
printf(Hello world");
return 0;
}

Output

输出量

prog.c: In function ‘main’:
prog.c:4:9: error: ‘Hello’ undeclared (first use in this function)printf(Hello world");^~~~~
prog.c:4:9: note: each undeclared identifier is reported only once
for each function it appears in
prog.c:4:15: error: expected ‘)’ before ‘world’printf(Hello world");^~~~~
prog.c:4:20: warning: missing terminating " characterprintf(Hello world");^
prog.c:4:20: error: missing terminating " characterprintf(Hello world");^~~
prog.c:6:1: error: expected ‘;’ before ‘}’ token}^

What happens, if we use single quote instead of double code in starting of the text/string?

如果我们在文本/字符串的开头使用单引号而不是双代码会怎样？

Missing terminating ' character error will be thrown.

缺少终止字符错误将被抛出。

How to fix?

怎么修？

To fix this error, close the text/string/Hello within the double quotes.

要解决此错误，请关闭双引号内的text / string / Hello。

Correct code:

正确的代码：

#include <stdio.h>
int main(void) {//closing double quote is missing
printf("Hello world");
return 0;
}

Output

输出量

Hello world

翻译自: https://www.includehelp.com/c-programs/hello-or-text-undeclared-while-printing-hello-world-using-printf-error-in-c.aspx