If a free registration is not available, these are then stored in the memory only. This makes the use of register variables to be much faster than that of the variables stored in the memory during the runtime of the program. The only difference is that the compiler tries to store these variables in the register of the microprocessor if a free register is available. This storage class declares register variables that have the same functionality as that of the auto variables. By default, they are assigned the value 0 by the compiler. Global static variables can be accessed anywhere in the program. Their scope is local to the function to which they were defined. Thus, no new memory is allocated because they are not re-declared. So we can say that they are initialized only once and exist till the termination of the program. Static variables have the property of preserving their value even after they are out of their scope! Hence, static variables preserve the value of their last use in their scope. This storage class is used to declare static variables which are popularly used while writing programs in C language. The main purpose of using extern variables is that they can be accessed between two different files which are part of a large program. This basically signifies that we are not initializing a new variable but instead, we are using/accessing the global variable only. It can be accessed within any function/block.Īlso, a normal global variable can be made extern as well by placing the ‘extern’ keyword before its declaration/definition in any function/block. So an extern variable is nothing but a global variable initialized with a legal value where it is declared in order to be used elsewhere. Basically, the value is assigned to it in a different block and this can be overwritten/changed in a different block as well. externĮxtern storage class simply tells us that the variable is defined elsewhere and not within the same block where it is used. They are assigned a garbage value by default whenever they are declared. However, they can be accessed outside their scope as well using the concept of pointers given here by pointing to the very exact memory location where the variables reside. Software Engineering Interview Questions.Top 10 System Design Interview Questions and Answers.Top 20 Puzzles Commonly Asked During SDE Interviews.Commonly Asked Data Structure Interview Questions. Top 10 algorithms in Interview Questions.Top 20 Dynamic Programming Interview Questions.Top 20 Hashing Technique based Interview Questions.Top 50 Dynamic Programming (DP) Problems.Top 20 Greedy Algorithms Interview Questions.Top 100 DSA Interview Questions Topic-wise.
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