The Differences in Malloc and Calloc
Malloc and calloc are two memory management functions in the “C” programming language. Programs do not need to reserve areas of memory, because that is usually the responsibility of the operating system. These two functions are not frequently used and are only needed for those programs that cannot rely on standard memory management processes.
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“C” Programming Language
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“C” has long been a favoured language for networking programming and file handling. It is a difficult language to learn, because its keywords are much more coded and less like real language than other languages such as COBOL, Pascal or Java. “C” is closely tied to the Unix operating system. In fact, Unix is written in “C.” Although Unix has its own scripting language, “C” is the prevalent language for programming Unix-based services. As memory allocation is closely related to operating systems, malloc and calloc are more likely to be found in low level services programmed in “C” than in client facing high level applications.
Memory Management
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A “C” program is a list of human-readable instructions that cannot be run on a computer. The program has to be compiled, which generates a copy of the program in machine-readable code. Operating systems usually allocate memory locations to the variables and instructions in the program at the time the program is compiled. Variables are a temporary storage space for data during the course of the program run. Malloc and calloc provide a method to delay allocation of memory addresses until the program runs. This is called dynamic memory management.
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Malloc and Calloc
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Both malloc and calloc allocate a space in heap memory to the program. Each function returns a pointer to the first allocated memory address and all other memory blocks should be contiguous. If the system does not have the memory available, both functions return null. Both functions reserve memory for either integer or character data. In each case, the memory block size should be a multiple of the size required for that data type. Therefore, it is common practice to use the sizeof() function within the parameter list for both malloc and calloc for the block size argument to ensure that the requested memory size is a multiple of the intended data type.
Comparison
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Malloc takes one argument and allocates one block of the requested size. Calloc takes two arguments, which are the number of blocks required and the required size for each block. For this reason, malloc is judged to be useful for a single variable, and calloc is better suited to allocating memory for an array -- which contains several elements. Malloc does not initialize the requested memory area, whereas calloc zero fills it.
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References
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