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Point out the error in the following program main() { const int x; x=128; printf("%d",x); }
x should have been initialized where it is declared.
shrutimitra
- Oct 23rd, 2005
We can not assign a value to a const variables. we can only initialize it while creating or declearing the variable.
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If the following program (myprog) is run from the command line as myprog monday tuesday wednesday thursday, What would be the output? main(int argc, char *argv[]) { while(--argc >0) printf("%s",*++argv); } a) myprog monday tuesday wednesday thursday b) monday tuesday wednesday thursday c) myprog tuesday thursday d) None of the above
shrutimitra
- Oct 23rd, 2005
B) monday tuesday wednesday thursday. Because in while loop we have (--argc) which will ensure that the loop will run for 4 times. if we want to print value of (*++argv) ,it will skip the first value of argv array.
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In the following code; #include<stdio.h> main() { FILE *fp; fp= fopen("trial","r"); } fp points to: a) The first character in the file. b) A structure which contains a "char" pointer which points to the first character in the file. c) The name of the file. d) None of the above.
shrutimitra
- Oct 23rd, 2005
B) A structure which contains a "char" pointer which points to the first character in the file.
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What is the difference between goto and longjmp() and setjmp()?
A goto statement implements a local jump of program execution, and the longjmp() and setjmp() functions implement a nonlocal, or far, jump of program execution. Generally, a jump in execution of any kind should be avoided because it is not considered good programming practice to use such statements as goto and longjmp in your program. A goto statement simply bypasses code in your program and jumps...
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What is #line used for?
The #line preprocessor directive is used to reset the values of the _ _LINE_ _ and _ _FILE_ _ symbols, respectively. This directive is commonly used in fourth-generation languages that generate C language source files.
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How many levels deep can include files be nested?
Even though there is no limit to the number of levels of nested include files you can have, your compiler might run out of stack space while trying to include an inordinately high number of files. This number varies according to your hardware configuration and possibly your compiler.
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When should the volatile modifier be used?
The volatile modifier is a directive to the compiler’s optimizer that operations involving this variable should not be optimized in certain ways. There are two special cases in which use of the volatile modifier is desirable. The first case involves memory-mapped hardware (a device such as a graphics adaptor that appears to the computer’s hardware as if it were part of the computer’s memory), and...
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How can you restore a redirected standard stream?
The preceding example showed how you can redirect a standard stream from within your program. But what if later in your program you wanted to restore the standard stream to its original state? By using the standard C library functions named dup() and fdopen(), you can restore a standard stream such as stdout to its original state. The dup() function duplicates a file handle. You can use the dup()...
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How do you determine whether to use a stream function or a low-level function?
Stream functions such as fread() and fwrite() are buffered and are more efficient when reading and writing text or binary data to files. You generally gain better performance by using stream functions rather than their unbuffered low-level counterparts such as read() and write(). In multi-user environments, however, when files are typically shared and portions of files are continuously being locked,...
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How can I open a file so that other programs can update it at the same time?
Your C compiler library contains a low-level file function called sopen() that can be used to open a file in shared mode. Beginning with DOS 3.0, files could be opened in shared mode by loading a special program named SHARE.EXE. Shared mode, as the name implies, allows a file to be shared with other programs as well as your own. Using this function, you can allow other programs that are running to...
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How can I make sure that my program is the only one accessing a file?
By using the sopen() function you can open a file in shared mode and explicitly deny reading and writing permissions to any other program but yours. This task is accomplished by using the SH_DENYWR shared flag to denote that your program is going to deny any writing or reading attempts by other programs. For example, the following snippet of code shows a file being opened in shared mode, denying...
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What will the preprocessor do for a program?
The C preprocessor is used to modify your program according to the preprocessor directives in your source code. A preprocessor directive is a statement (such as #define) that gives the preprocessor specific instructions on how to modify your source code. The preprocessor is invoked as the first part of your compiler program’s compilation step. It is usually hidden from the programmer because it is...
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How can you avoid including a header more than once?
One easy technique to avoid multiple inclusions of the same header is to use the #ifndef and #define preprocessor directives. When you create a header for your program, you can #define a symbolic name that is unique to that header. You can use the conditional preprocessor directive named #ifndef to check whether that symbolic name has already been assigned. If it is assigned, you should not include...
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What is the benefit of using an enum rather than a #define constant?
The use of an enumeration constant (enum) has many advantages over using the traditional symbolic constant style of #define. These advantages include a lower maintenance requirement, improved program readability, and better debugging capability. 1) The first advantage is that enumerated constants are generated automatically by the compiler. Conversely, symbolic constants must be manually...
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