-
Notifications
You must be signed in to change notification settings - Fork 2
Expand file tree
/
Copy pathstorage-class.html
More file actions
635 lines (524 loc) · 26.5 KB
/
storage-class.html
File metadata and controls
635 lines (524 loc) · 26.5 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<meta name="description" content="Storage class determine two things of the variable i.e. lifetime(how
long the variable be in the memory) and scope(from where, till where we
can access the variable)." />
<meta name="keywords"
content="storage class, storage class in cpp, storage class in c++, what is a storage class in cpp, what is a storage class in c++, what is a storage class, use of storage class, c++, cpp" />
<title>C++ Storage Class | C++ Tutorials | CodeMistic</title>
<!-- Google Ad -->
<script data-ad-client="ca-pub-5352867889640158" async
src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>
<!-- Google Tag Manager -->
<script>(function (w, d, s, l, i) {
w[l] = w[l] || []; w[l].push({
'gtm.start':
new Date().getTime(), event: 'gtm.js'
}); var f = d.getElementsByTagName(s)[0],
j = d.createElement(s), dl = l != 'dataLayer' ? '&l=' + l : ''; j.async = true; j.src =
'https://www.googletagmanager.com/gtm.js?id=' + i + dl; f.parentNode.insertBefore(j, f);
})(window, document, 'script', 'dataLayer', 'GTM-MCNC43J');</script>
<!-- End Google Tag Manager -->
<!-- Global site tag (gtag.js) - Google Analytics -->
<script async src="https://www.googletagmanager.com/gtag/js?id=G-YPTQSLH0XW"></script>
<script>
window.dataLayer = window.dataLayer || [];
function gtag() { dataLayer.push(arguments); }
gtag('js', new Date());
gtag('config', 'G-YPTQSLH0XW');
</script>
<!-- Favicon -->
<link rel="icon" type="img/png" href="../favicon.png" />
<!-- FONT AWESOME -->
<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.13.1/css/all.css"
integrity="sha384-xxzQGERXS00kBmZW/6qxqJPyxW3UR0BPsL4c8ILaIWXva5kFi7TxkIIaMiKtqV1Q" crossorigin="anonymous" />
<!-- FONTS -->
<link href="https://fonts.googleapis.com/css2?family=Kalam:wght@700&family=Ubuntu&family=Varela+Round&display=swap"
rel="stylesheet" />
<!-- Animate on scroll -->
<link rel="stylesheet" href="https://unpkg.com/aos@next/dist/aos.css" />
<!-- Bootstrap -->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css"
integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous" />
<!-- CSS -->
<link rel="stylesheet" href="../lang_styles.css" />
</head>
<body>
<!-- Google Tag Manager (noscript) -->
<noscript><iframe src="https://www.googletagmanager.com/ns.html?id=GTM-MCNC43J" height="0" width="0"
style="display:none;visibility:hidden"></iframe></noscript>
<!-- End Google Tag Manager (noscript) -->
<!-- NAVIGATION BAR -->
<!-- <div class="container-fluid"> -->
<nav class="navbar fixed-top navbar-expand-xl navbar-dark">
<a class="navbar-brand" href="../index.html">CODEMISTIC</a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent"
aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarSupportedContent">
<ul class="navbar-nav ml-auto">
<li class="nav-item">
<a class="nav-link" href="../index.html">Home</a>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button"
data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
Tutorials
</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="../cpp.html">C++</a>
<div class="dropdown-divider"></div>
<a class="dropdown-item" href="../python.html">Python</a>
<div class="dropdown-divider"></div>
<a class="dropdown-item" href="../java.html">Java</a>
<div class="dropdown-divider"></div>
<a class="dropdown-item" href="../dsa.html">Data Structure and Algorithms</a>
<div class="dropdown-divider"></div>
<a class="dropdown-item" href="../tutorials.html">All Tutorials</a>
</div>
</li>
<li class="nav-item">
<a class="nav-link" href="../events.html">Events</a>
</li>
<li class="nav-item">
<a class="nav-link" href="../teen-code.html">Teen-Code</a>
</li>
<li class="nav-item">
<a class="nav-link" href="../campus.html">Campus Programme</a>
</li>
<!-- <li class="nav-item">
<a class="nav-link" href="https://docs.google.com/forms/d/e/1FAIpQLSc2O28YJpxQc6kh2tKpI_Lf5MwfwGXVnhMs0g5EEXobJ4Beeg/viewform?usp=sf_link" target="_blank">Contribute</a>
</li> -->
<li class="nav-item">
<a class="nav-link" href="../register.html">Join Our Community</a>
</li>
</ul>
</div>
</nav>
<!-- Accordion -->
<section class="lbar">
<div class="lang-img col-md-2">
<img src="../logo/cpp.png" alt="c++" class="cpp-img" style="margin-left: -25px;">
</div>
<ul id="accordion" class="accordion ml-5">
<li class=" collape in">
<div class="link">C++ Introduction<i class="fa fa-chevron-down"></i>
</div>
<ul class="submenu collapse">
<li>
<a href="getting-started.html" class="closed">Getting Started</a>
</li>
<li>
<a href="variables-and-literals.html " class="closed">C++ Variables and Literals</a>
</li>
<li>
<a href="data-types.html" class="closed">C++ Data Types</a>
</li>
<li>
<a href="input-output.html" class="closed">C++ Basic I/O</a>
</li>
<li>
<a href="type-conversion.html" class="closed">C++ Type Conversion</a>
</li>
<li>
<a href="operators.html" class="closed">C++ Operators</a>
</li>
<li>
<a href="comments.html" class="closed">C++ Comments</a>
</li>
</ul>
</li>
<li>
<div class="link">C++ Flow Control<i class="fa fa-chevron-down"></i>
</div>
<ul class="submenu collapse">
<li>
<a href="if-else.html" class="closed">C++ if...else</a>
</li>
<li>
<a href="for-loop.html" class="closed">C++ for Loop</a>
</li>
<li>
<a href="do-while.html" class="closed">C++ do...while Loop</a>
</li>
<li>
<a href="break-and-continue.html" class="closed">C++ break & continue</a>
</li>
<li>
<a href="switch-statement.html" class="closed">C++ switch Statement</a>
</li>
<li>
<a href="goto-statement.html" class="closed">C++ goto Statement</a>
</li>
</ul>
</li>
<li>
<div class="link">C++ Function<i class="fa fa-chevron-down"></i>
</div>
<ul class="submenu collapse show">
<li>
<a href="functions.html" class="closed">C++ Functions</a>
</li>
<li>
<a href="function-types.html" class="closed">C++ Function Types</a>
</li>
<li>
<a href="function-overloading.html" class="closed">C++ Function Overloading</a>
</li>
<li>
<a href="default-argument.html" class="closed">C++ Default Argument</a>
</li>
<li>
<a href="storage-class.html" class="opened">C++ Storage Class</a>
</li>
<li>
<a href="recursion.html" class="closed">C++ Recursion</a>
</li>
<li>
<a href="return-reference.html" class="closed">C++ Return Reference</a>
</li>
</ul>
</li>
<li>
<div class="link">C++ Arrays & String<i class="fa fa-chevron-down"></i>
</div>
<ul class="submenu collapse">
<li>
<a href="arrays.html" class="closed">C++ Arrays</a>
</li>
<li>
<a href="multidimensional-arrays.html" class="closed">C++ Multidimensional Arrays</a>
</li>
<li>
<a href="function-arrays.html" class="closed">C++ Function and Array</a>
</li>
<li>
<a href="string.html" class="closed">C++ String</a>
</li>
</ul>
</li>
<li>
<div class="link">C++ Structures<i class="fa fa-chevron-down"></i>
</div>
<ul class="submenu collapse">
<li>
<a href="structures.html" class="closed">C++ Structures</a>
</li>
<li>
<a href="structure-fuction.html" class="closed">Structure and Function</a>
</li>
<li>
<a href="pointers-structures.html" class="closed">C++ Pointers to Structure</a>
</li>
<li>
<a href="enumeration.html" class="closed">C++ Enumeration</a>
</li>
</ul>
</li>
<li>
<div class="link">C++ Object & Class<i class="fa fa-chevron-down"></i>
</div>
<ul class="submenu collapse">
<li>
<a href="object-class.html" class="closed">C++ Objects and Class</a>
</li>
<li>
<a href="constructors.html" class="closed">C++ Constructors</a>
</li>
<li>
<a href="objects-fuctions.html" class="closed">C++ Objects & Function</a>
</li>
<li>
<a href="operator-overloading.html" class="closed">C++ Operator Overloading</a>
</li>
</ul>
</li>
<li>
<div class="link">C++ Pointers<i class="fa fa-chevron-down"></i>
</div>
<ul class="submenu collapse">
<li>
<a href="pointers.html" class="closed">C++ Pointers</a>
</li>
<li>
<a href="pointers-arrays.html" class="closed">C++ Pointers and Arrays</a>
</li>
<li>
<a href="pointers-functions.html" class="closed">C++ Pointers and Functions</a>
</li>
<li>
<a href="memory-management.html" class="closed">C++ Memory Management</a>
</li>
</ul>
</li>
<li>
<div class="link">C++ Inheritance<i class="fa fa-chevron-down"></i>
</div>
<ul class="submenu collapse">
<li>
<a href="inheritance.html" class="closed">C++ Inheritance</a>
</li>
<li>
<a href="inheritance-access-control.html" class="closed">Inheritance Access Control</a>
</li>
<li>
<a href="function-overriding.html" class="closed">C++ Function Overriding</a>
</li>
<li>
<a href="inheritence-types.html" class="closed">Inheritance Types</a>
</li>
<li>
<a href="friend-function.html" class="closed">C++ Friend Function</a>
</li>
<li>
<a href="virtual-function.html" class="closed">C++ Virtual Function</a>
</li>
<li>
<a href="templates.html" class="closed">C++ Templates</a>
</li>
</ul>
</li>
</ul>
</section>
<br>
<section class="para">
<!-- <div class="but mt-4">
<button class="btn btn-md btn-primary "><a href="../dsa.html"><i
class="fas fa-arrow-left "></i> Back to Index</a></button>
</div> -->
<!-- breadcrumb -->
<nav class="bdcrumb" id="bdcrumb" aria-label="breadcrumb">
<ul class="breadcrumb">
<li class="breadcrumb-item"><a href="../tutorials.html"><i class="fas fa-home"></i></a></li>
<li class="breadcrumb-item"><a href="../cpp.html">C++ Tutorials</a></li>
<li class="breadcrumb-item active" aria-current="page">C++ Storage Class</li>
</ul>
</nav>
<!-- breadcrumb ending -->
<!-- HEADING -->
<div class="wrapper">
<h3 class="pb-3 pt-3">C++ Storage Class</h3>
<p>In this article,we are going to learn about storage class.</p>
<p>Every variable in C++ has two features: type and storage class.</p>
<p>Type specifies that what kind of data can be stored in a variable. For
example: <code>int</code>, <code>float</code>, <code>char</code> etc.</p>
<p>And, storage class determine two things of the variable i.e. lifetime (how
long the variable be in the memory) and scope (from where, till where we
can access the variable).</p>
<p>Depending upon the storage class of a variable, it can be divided into 4
major types :</p>
<ol>
<li>
Local variable
</li>
<li>
Global variable
</li>
<li>
Static local variable
</li>
<li>
Register Variable
</li>
<li>
Thread Local Storage
</li>
</ol>
<div class="if-content-img d-flex flex-column m-5">
<img class="if-content m-auto" src="images/storage-class-1.jpg" alt="" />
</div>
<hr />
<h4 class="pt-3 pb-3">Local Variable</h4>
<p>A local variable is defined inside a function (i.e. inside the braces of the
function definition) and it can only be accessed within that function this is
called local or automatic variable.</p>
<p>Its scope is limited to that function only (i.e. it can’t be accessed from
outside the function body in which it is declared).</p>
<p>The life of the variable gets finished as soon as that function is ended in
other words we can say that it gets erased from the memory as soon as the
function end.</p>
<hr />
<h4 class="pt-3 pb-3">Global Variable</h4>
<p>When a variable is declared outside all the functions it is said to be a global
variable.</p>
<p>Its scope is valid in whole program that is it can be accessed from
anywhere and by anyone in the whole program.</p>
<p>Like it's scope, its lifetime is also valid throughout the program that is it will
have a storage in memory from the start of the program till the termination
of the program.</p>
<hr />
<p><strong>Example 1:</strong></p>
<pre>#include <iostream>
using namespace std;
// Global variable declaration
int count = 12;
void example();
void example2();
int main() {
++count;
// Outputs 13
cout << count << endl;
example();
example2();
return 0;
}
void example() {
int i = 9;
++count;
++i;
// Outputs 10
cout << i;
// Outputs 14
cout << count;
}
void example2() {
++count;
++i;
// invalid code
cout << i;
// Outputs 15
cout << count;
}</pre>
<p>In the above program, <code>count</code> is a global variable and <code>i</code> is the local variable
for the function <code>example()</code>. So, the variable count is available for each and
every function in the program but variable <code>i</code> is only available for the function
<code>example()</code> and it cannot be used outside anywhere except inside the
braces of function <code>example()</code>. So it will generate error when we will use it
inside <code>example2()</code> or anywhere except <code>example()</code>.The error that compiler
will generate <strong>undefined symbol 'i</strong> when we use it inside <code>example2()</code>.</p>
<hr />
<h4 class="pt-3 pb-3">Static Local Variable</h4>
<p>Keyword static is used for specifying a static variable. For example :</p>
<pre>... .. ...
int main()
{
static float a;
... .. ...
}</pre>
<p>A static local variable scope is limited to that function in which it is defined
same as that of local variable but its lifetime is throughout the program that
is its last value resides in the memory after the function’s execution is
terminated.</p>
<p>For more clarity let’s take an example :</p>
<pre>#include <iostream>
using namespace std;
void example() {
// var is a static variable
static int count = 2;
++count;
cout << count << endl;
}
int main() {
example();
example();
return 0;
}</pre>
<p><strong>Output :</strong></p>
<pre>3
4</pre>
<p>In the above program, <code>example()</code> function is invoked <strong>2 times</strong>.</p>
<p>During the first call, variable <code>count</code> is declared as static variable and
initialized to <strong>0</strong>. Then <strong>1</strong> is added to <code>count</code> which is
displayed in the screen.
When the function <code>example()</code> returns, the variable <code>var</code> should be
<strong>2</strong> but since
the variable <code>var</code> is a static variable it's last value was still inside the memory.So,
during second function call, no new variable <code>var</code> is created. The same <code>var</code> is
increased by <strong>1</strong> and then displayed to the screen.</p>
<hr />
<h4 class="pt-3 pb-3">Register Variable</h4>
<p>Keyword <code>register</code> is used for specifying register variables</p>
<p>Register variables are similar to automatic variables and exists inside a
particular function only. It is supposed to be faster than the local variables.</p>
<p>If a program encounters a register variable, it stores the variable in
processor's register rather than memory if available. This makes it faster
than the local variable.</p>
<hr/>
<h4 class="pt-3 pb-3">Thread Local Storage</h4>
<p><strong>Thread-local storage</strong> is a mechanism by which variables are allocated such
that there is one instance of the variable per extant thread.</p>
<p>Keyword <code>thread_local</code> is used for this purpose.</p>
</div>
<div class="but text-right">
<button class="btn btn-primary pull-right"><a href="recursion.html">Next Topic <i
class="fas fa-arrow-right "></i><br />C++ Recursion</a></button>
</div><br />
</section>
<!-- footer -->
<footer>
<div class="row footer">
<div class="logo">
<img src="../image.png" alt="" class="f-img">
<h5>LEARN CODE DISCUSS</h5>
</div>
<div class="footer-column ">
<ul class="footer-ul">
<li class="foot-header"><strong>CodeMistic</strong></li>
<li class="f-li"><a href="../index.html" class="f-links">Home</a></li>
<li class="f-li"><a href="../team.html" class="f-links">Our Team</a></li>
<li class="f-li"><a href="../terms-and-conditions.html" class="f-links">Terms of Service</a></li>
<li class="f-li"><a href="../privacy-policy.html" class="f-links">Privacy Policy</a></li>
</ul>
</div>
<div class="footer-column ">
<ul class="footer-ul ">
<li class="foot-header"><strong>LEARN</strong></li>
<li class="f-li"><a href="../cpp.html" class="f-links">C++</a></li>
<li class="f-li"><a href="../java.html" class="f-links">Java</a></li>
<li class="f-li"><a href="../python.html" class="f-links">Python</a></li>
<li class="f-li"><a href="../dsa.html" class="f-links">DSA</a></li>
</ul>
</div>
<div class="footer-column ">
<ul class="footer-ul ">
<li class="foot-header"><strong>CONTRIBUTE</strong></li>
<li class="f-li"><a
href="https://docs.google.com/forms/d/e/1FAIpQLSduxk_aP9M1lqUAebQJwRXiVm2ukmdgv3T7gjBpOsr_gdeOcQ/viewform?usp=sf_link"
class="f-links" target="_blank">Write an Article/Blog</a></li>
<li class="f-li"><a
href="https://docs.google.com/forms/d/e/1FAIpQLSc2O28YJpxQc6kh2tKpI_Lf5MwfwGXVnhMs0g5EEXobJ4Beeg/viewform?usp=sf_link"
class="f-links" target="_blank">Internships</a></li>
<li class="f-li"><a
href="https://docs.google.com/forms/d/e/1FAIpQLSe9nr_Aw0fGIqm3_xWhqEzTr3UWdOFz-pvKpQvkAsosORYq9w/viewform?usp=sf_link"
class="f-links" target="_blank">Videos</a></li>
<li class="f-li"><a
href="https://docs.google.com/forms/d/e/1FAIpQLScOW3hJjxxwzPYL4u51oboc4T1aDtIUEIRa20hKPKu4UlcZAA/viewform?usp=sf_link"
class="f-links" target="_blank">Donations/Funds</a></li>
</ul>
</div>
</div>
<div class="footer-links" style="text-align: center;">
<!-- <h7>Connect With Us</h7><br><br> -->
<a href="https://www.facebook.com/codemistic " target="_blank "><i class="icons fa-2x fab fa-facebook "
style="color:#3b5998; "></i></a>
<a href="https://www.instagram.com/codemistic " target="_blank "><i class="icons fa-2x fab fa-instagram "
style="color:#e95950; "></i></a>
<a href="https://www.twitter.com/codemistic " target="_blank "><i class="icons fa-2x fab fa-twitter "
style="color:#8accf5; "></i></a>
<a href="https://www.linkedin.com/company/codemistic " target="_blank "><i
class="icons fa-2x fab fa-linkedin " style="color:#88b3ee; "></i></a>
<a href="https://t.me/codemistic " target="_blank "><i class="icons fa-2x fab fa-telegram "
style="color:#65adda; "></i></a>
<a href="https://www.youtube.com/channel/UCS1Iv_kkgQGDwoXtvrlwlag " target="_blank "><i
class="icons fa-2x fab fa-youtube " style="color:red; "></i></a>
<p class="foot mt-3">© Copyright : <strong>CodeMistic</strong> All Rights Reserved.</p>
</div>
</footer>
<!-- CSS Scripts -->
<script src="https://code.jquery.com/jquery-3.5.1.slim.min.js "
integrity="sha384-DfXdz2htPH0lsSSs5nCTpuj/zy4C+OGpamoFVy38MVBnE+IbbVYUew+OrCXaRkfj "
crossorigin="anonymous "></script>
<script src="https://cdn.jsdelivr.net/npm/popper.js@1.16.0/dist/umd/popper.min.js "
integrity="sha384-Q6E9RHvbIyZFJoft+2mJbHaEWldlvI9IOYy5n3zV9zzTtmI3UksdQRVvoxMfooAo "
crossorigin="anonymous "></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.5.0/js/bootstrap.min.js "
integrity="sha384-OgVRvuATP1z7JjHLkuOU7Xw704+h835Lr+6QL9UvYjZE3Ipu6Tp75j7Bh/kR0JKI "
crossorigin="anonymous "></script>
<script src='https://cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js'></script>
<script src='../side.js'></script>
</body>
</html>