c – C Programming Language

C has inspired various other languages. Languages that are extensions of C include C++ and Objective-C.

Major interpreters and virtual machines written in C:

• CPython (Python)
• Ruby MRI (Ruby)
• Zend Engine (PHP)

Major operating systems written in C:

• Unix
• BSD
• Linux
• Windows
• Darwin (Mac OS X, iOS)

Major systems writtin in C:

• Postgres
• Redis
• Memcached
• Nginx
• Apache

You really should know C. I recommend learning C before C++ or Objective-C.

Memory

Memory management is what makes C (and C++) a significantly different beast. Precautions must be taken, even by programmers transitioning from C++.

• & is “address of” – use on variable to get its memory address
• * is “dereference” – use on pointer variable to get/set value
• -> is “access member” – use with struct/union to access member variable. Recall that it is sugar for dotting into dereferenced variable

Use malloc to dynamically allocate memory on the heap:

• e.g. int* integers = (int*) malloc(sizeof(int) * 10);
• only argument is the number of bytes to allocate
• calculate bytes by multiplying sizeof data type by number of that data
  • e.g. sizeof(int) * 10 for an integer array of 10
• returns void* (void pointer) which you should cast
• remember it DOES NOT initialize the array
• remember to deallocate memory using free function
• remember to set pointer to NULL after freeing memory

REFERENCES

C dynamic memory allocation. Wikipedia.

Dangling pointer Wikipedia.

malloc. Linux man page. Covers malloc, free, calloc, realloc.

Troubleshooting Segmentation Violations/Faults