CS计算机代考程序代写 data structure compiler Microsoft PowerPoint - 05_MemoryMaps.pptx

Microsoft PowerPoint – 05_MemoryMaps.pptx

CS 2211
Systems Programming

Part Four:
Memory Maps

1 2

COMPUTER MEMORY

1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 1

0 0 1 0 0 0 1 1 0 1 1 0 0 1 1 1 0 0 1 1 0 1 1 1

0 1 0 1 0 1 1 1 1 0 1 0 1 0 1 1 0 1 0 0 0 1 1 0

1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 0 1 0

0 0 1 0 0 0 1 1 0 1 1 0 0 1 1 1 0 0 1 1 0 1 1 1

1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 1

1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 0 1 0

0 1 0 1 0 1 1 1 1 0 1 0 1 0 1 1 0 1 0 0 0 1 1 0

1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 1

1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 0 1 0

COMPUTER MEMORY

1 2

3 4

1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 1

0 0 1 0 0 0 1 1 0 1 1 0 0 1 1 1 0 0 1 1 0 1 1 1

0 1 0 1 0 1 1 1 1 0 1 0 1 0 1 1 0 1 0 0 0 1 1 0

1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 0 1 0

0 0 1 0 0 0 1 1 0 1 1 0 0 1 1 1 0 0 1 1 0 1 1 1

1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 1

1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 0 1 0

0 1 0 1 0 1 1 1 1 0 1 0 1 0 1 1 0 1 0 0 0 1 1 0

1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 1

1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 0 1 0

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 –

COMPUTER MEMORY

1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 1

0 0 1 0 0 0 1 1 0 1 1 0 0 1 1 1 0 0 1 1 0 1 1 1

0 1 0 1 0 1 1 1 1 0 1 0 1 0 1 1 0 1 0 0 0 1 1 0

1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 0 1 0

0 0 1 0 0 0 1 1 0 1 1 0 0 1 1 1 0 0 1 1 0 1 1 1

1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 1

1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 0 1 0

0 1 0 1 0 1 1 1 1 0 1 0 1 0 1 1 0 1 0 0 0 1 1 0

1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 1

1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 0 1 0

COMPUTER MEMORY

397 – 398 – 399 –
1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 1
400 – 401 – 402 –
0 0 1 0 0 0 1 1 0 1 1 0 0 1 1 1 0 0 1 1 0 1 1 1
403 – 404 – 405 –
0 1 0 1 0 1 1 1 1 0 1 0 1 0 1 1 0 1 0 0 0 1 1 0
406 – 407 – 408 –
1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 0 1 0
409 – 410 – 411 –
0 0 1 0 0 0 1 1 0 1 1 0 0 1 1 1 0 0 1 1 0 1 1 1
412 – 413 – 414 –
1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 1
415 – 416 – 417 –

1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 0 1 0
418 – 419 – 420 –
0 1 0 1 0 1 1 1 1 0 1 0 1 0 1 1 0 1 0 0 0 1 1 0
421 – 422 – 423 –
1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 1

COMPUTER MEMORY MEMORY MAPPING

char a, b, c;

Type Label Address Value Binary

399
400
401
402
403
404
405
406
…

5 6

7 8

Type Label Address Value Binary

399
char a 400
char b 401
char c 402

403
404
405
406
…

MEMORY MAPPING

char a, b, c; /* char – 1 byte each */

Type Label Address Value Binary

399
char a 400
char b 401
char c 402

403
404
405
406
…

MEMORY MAPPING

char a, b, c; /* char – 1 byte each */

Side bar:

actual computer addresses
reflect the size of the available
memory.

Actual addresses look like:
140727232603148
140727232603149
140727232603150

( -or displayed in hex:
0x7ffd9cb5a40c
0x7ffd9cb5a40d
0x7ffd9cb5a40e )

To make it easier to use and
understand, we will use
artificially small numbers like:

400 – 401 – 402 etc.

Type Label Address Value Binary

399
char a 400

401
402

char c 403
404

char b 405
406
…

MEMORY MAPPING

char a, b, c; /* char – 1 byte each */

note: not necessarily contiguous
assigned to locations that are ‘free’
and available for the size required.

Type Label Address Value Binary

399
char a 400
char b 401
char c 402

403
404
405
406
…

MEMORY MAPPING

char a, b, c; /* char – 1 byte each */

9 10

11 12

MEMORY MAPPING

char a, b, c; /* char – 1 byte each */

Type Label Address Value Binary

399
char a 400
char b 401
char c 402

403
404
405
406
…

MEMORY MAPPING

char a, b, c; /* char – 1 byte each */
a = 7; /* (0000 0111) */
b = -13; /* (1111 0011) */
c = 0; /* (0000 0000) */

Type Label Address Value Binary

399
char a 400 7 0000 0111
char b 401 -13 1111 0011
char c 402 0 0000 0000

403
404
405
406
…

Memory Maps

END OF PART 1

MEMORY MAPPING

char a = 7;
/* char: 1 byte */

Side bar:

char a = 7;

[ variable declaration
– AND –

variable definition ]

(computer process this as two
separate statements)

1.) char a;
2. ) a = 7;

Type Label Address Value Binary

399

400

401

402

403

404

405

406

407

408

409

410

411

412

413

414

415

416

417

418

…

13 14

15 16

MEMORY MAPPING

char a = 7;
/* char: 1 byte */

Side bar:

char a = 7;

[ variable declaration
– AND –

variable definition ]

(computer process this as two
separate statements)

1.) char a;
2. ) a = 7;

Type Label Address Value Binary

399

400

401

402

403

404

405

406

407

408

409

410

411

412

413

414

415

416

417

418

…

MEMORY MAPPING

char a = 7;
/* char: 1 byte */

Side bar:

char a = 7;

[ variable declaration
– AND –

variable definition ]

(computer process this as two
separate statements)

1.) char a;
2. ) a = 7;

Type Label Address Value Binary

399

400

401

402

403

404

405

406

407

408

409

410

411

412

413

414

415

416

417

418

…

Type Label Address Value Binary

399

char a 400 7 0000 0111

int b 401 -13 1111 1111

402 1111 1111

403 1111 1111

404 1111 0011

float c 405 0.1 0011 1110

406 0000 0000

407 0000 0000

408 0000 0000

double d 409 42.5 0100 0000

410 0100 0101

411 0100 0000

412 0000 0000

413 0000 0000

414 0000 0000

415 0000 0000

416 0000 0000

417

418

…

MEMORY MAPPING

char a = 7;
/* char: 1 byte */

int b = -13;
/* int: 4 bytes */

float c = 0.1;
/* float: 4 bytes */

double d = 42.5;
/* double: 8 bytes */

MEMORY MAPPING

char a = 7;
/* char: 1 byte */

int b = -13;
/* int: 4 bytes */

float c = 0.1;
/* float: 4 bytes */

double d = 42.5;
/* double: 8 bytes */

Type Label Address Value Binary

399

char a 400 7 0000 0111

int b 401 -13 1111 1111

402 1111 1111

403 1111 1111

404 1111 0011

float c 405 0.1 0011 1110

406 0000 0000

407 0000 0000

408 0000 0000

double d 409 42.5 0100 0000

410 0100 0101

411 0100 0000

412 0000 0000

413 0000 0000

414 0000 0000

415 0000 0000

416 0000 0000

417

418

…

17 18

19 20

Label Address Value

399
a 400 7
b 401 – 404 -13
c 405 – 408 0.1
d 409 – 416 42.5

417
418
419
…

MEMORY MAPPING

char a;
int b;
float c;
double d;

a = 7; /* 1 byte */
b = -13; /* 4 bytes */
c = 0.1; /* 4 bytes */
d = 42.5; /* 8 bytes */

A BETTER WAY OF VISUALIZING THE MAP:

Memory Maps

END OF PART 2

Label Address Value

399
a 400

…

d 409 – 416
…

b 510 – 513

…
c 605 – 608

…

…
…

MEMORY MAPPING

char a;
int b;
float c;
double d;

ALLOCATION NOT NECESSARILY CONTIGOUS:

Label Address Value

399
a 400 7

…
d 409 – 416 42.5

…
b 510 – 513 -13

…
c 605 – 608 0.1

…

…
…

MEMORY MAPPING

char a;
int b;
float c;
double d;

a = 7; /* 1 byte */
b = -13; /* 4 bytes */
c = 0.1; /* 4 bytes */
d = 42.5; /* 8 bytes */

ALLOCATION NOT NECESSARILY CONTIGOUS:

21 22

23 24

Label Address Value

399
a 400 7

…

d 409 – 416 42.5

…

b 510 – 513 -13

…
c 605 – 608 0.1

…

…
…

MEMORY MAPPING

char a;
int b;
float c;
double d;

a = 7; /* 1 byte */
b = -13; /* 4 bytes */
c = 0.1; /* 4 bytes */
d = 42.5; /* 8 bytes */

ALLOCATION NOT NECESSARILY CONTIGOUS:
397 – 398 – 399 –
1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 1
400 – 401 – 402 –
0 0 1 0 0 0 1 1 0 1 1 0 0 1 1 1 0 0 1 1 0 1 1 1
403 – 404 – 405 –
0 1 0 1 0 1 1 1 1 0 1 0 1 0 1 1 0 1 0 0 0 1 1 0
406 – 407 – 408 –
1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 0 1 0
409 – 410 – 411 –
0 0 1 0 0 0 1 1 0 1 1 0 0 1 1 1 0 0 1 1 0 1 1 1
412 – 413 – 414 –
1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 1
415 – 416 – 417 –
1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 0 1 0
418 – 419 – 420 –
0 1 0 1 0 1 1 1 1 0 1 0 1 0 1 1 0 1 0 0 0 1 1 0
421 – 422 – 423 –
1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 1 1 0 0 0 1 1 0 1

Label Address Value

399
a 400

…

d 409 – 416

…

b 510 – 513

…
c 605 – 608

…

…
…

MEMORY MAPPING

char a;
int b;
float c;
double d;

VARIABLE DECLARATION VS. VARIABLE DEFINITION:

VARIABLE DECLARATION:
the variable is only declared

and allocated a block of memory
but still has no value

Label Address Value

399
a 400 7

…

d 409 – 416 42.5

…

b 510 – 513 -13

…
c 605 – 608 0.1

…

…
…

MEMORY MAPPING

a = 7; /* 1 byte */
b = -13; /* 4 bytes */
c = 0.1; /* 4 bytes */
d = 42.5; /* 8 bytes */

VARIABLE DEFINITION:
to assign or initialize it with

some specific value

VARIABLE DECLARATION VS. VARIABLE DEFINITION:

Memory Maps

END OF PART 3

25 26

27 28

MEMORY MAPPING

Scalar Variables versus Aggregate Variables

So far, the only variables we’ve seen are scalar: capable of holding a single data item.

C also supports aggregate variables, which can store collections of values.

There are two kinds of aggregates in C: arrays and structures.

We will start by looking at one-dimensional arrays,
which play a much bigger role in C than do multidimensional arrays.

An array is a data structure containing a number of data values, all of which have the
same type.

These values, known as elements, can be individually selected by their position within
the array.

The elements of a one-dimensional array a are conceptually arranged
one after another in a single row (or column):

MEMORY MAPPING

Scalar Variables versus Aggregate Variables

To declare an array, we must specify the type of the array’s elements and the number of elements:
int a[10];

The elements may be of any type; the length of the array can be any (integer) constant expression.

An array, like any other variable, can be given an initial value at the time it’s declared.
The most common form of array initializer is a list of constant expressions enclosed in braces and
separated by commas:

int a[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

If the initializer is shorter than the array, the remaining elements of the array are given the value 0:
int a[10] = {1, 2, 3, 4, 5, 6};
/* initial value of a is {1, 2, 3, 4, 5, 6, 0, 0, 0, 0} */

If an initializer is present, the length of the array may be omitted:
int a[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

The compiler uses the length of the initializer to determine how long the array is.

MEMORY MAPPING [ ARRAYS ]

int a[2];
/* int: 4 bytes */

float b[3];
/* float: 4 bytes */

double c[4];
/* double: 8 bytes */

char d[6];
/* char: 1 byte */

Label Address Value

a[0] 400 – 403
a[1] 404 – 407
b[0] 408 – 411
b[1] 412 – 415
b[2] 416 – 419
c[0] 420 – 427
c[1] 428 – 435
c[2] 436 – 443
c[3] 444 – 451
d[0] 452
d[1] 453
d[2] 454
d[3] 455
d[4] 456
d[5] 457

int a[2];

float b[3];

double c[4];

char d[6];

MEMORY MAPPING [ ARRAYS ]

int a[2] = {37, 52};
/* int: 4 bytes */

float b[3] = {26, 54};
/* float: 4 bytes */

double c[4];
/* double: 8 bytes */

char d[6];
/* char: 1 byte */

c[2] = 14.7;

Label Address Value

a[0] 400 – 403 37
a[1] 404 – 407 52
b[0] 408 – 411 26
b[1] 412 – 415 54
b[2] 416 – 419 0
c[0] 420 – 427 ?
c[1] 428 – 435 ?
c[2] 436 – 443 14.7
c[3] 444 – 451 ?
d[0] 452 ?
d[1] 453 ?
d[2] 454 ?
d[3] 455 ?
d[4] 456 ?
d[5] 457 ?

…

int a[2];

float b[3];

double c[4];

char d[6];

29 30

31 32

MEMORY MAPPING [ ARRAYS ]

int a[2] = {37, 52};
/* int: 4 bytes */

float b[3] = {26, 54};
/* float: 4 bytes */

double c[4];
/* double: 8 bytes */

char d[6];
/* char: 1 byte */

c[2] = 14.7;

d[4] = ‘a’;

/* BUT !now what happens if:
(because – this will compile
and run) */

b[4] = 15.9;
/* memory location 424-427 */

Label Address Value

a[0] 400 – 403 37
a[1] 404 – 407 52
b[0] 408 – 411 26
b[1] 412 – 415 54
b[2] 416 – 419 0
c[0] 420 424 – 427 ? 15.9
c[1] 428 – 435 ?
c[2] 436 – 443 14.7
c[3] 444 – 451 ?
d[0] 452 ?
d[1] 453 ?
d[2] 454 ?
d[3] 455 ?
d[4] 456 a
d[5] 457 ?

…

int a[2];

float b[3];

double c[4];

char d[6];

MEMORY MAPPING [ ARRAYS ]

int a[2] = {37, 52};
/* int: 4 bytes */

float b[3] = {26, 54};
/* float: 4 bytes */

double c[4];
/* double: 8 bytes */

char d[6];
/* char: 1 byte */

c[2] = 14.7;

d[4] = ‘a’;

/* OR !! This */

b[3333] = 15.9;
/* memory location 15205 */
run time error :
out of program allowed bounds

int a[2];

float b[3];

double c[4];

char d[6];

Label Address Value

b[3333]

15205

15.9

MEMORY MAPPING [ ARRAYS ]

int a[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

Label Address Value

a[0] 400 – 403 1
a[1] 404 – 407 2
a[2] 408 – 411 3
a[3] 412 – 415 4
a[4] 416 – 417 5
a[5] 420 – 421 6
a[6] 424 – 425 7
a[7] 428 – 431 8
a[8] 432 – 435 9
a[9] 436 – 439 10

If an initializer is present,
the length of the array may be omitted:

The compiler uses the length of the initializer
to determine how long the array is.

Memory Maps

END OF PART 4

33 34

35 36

MEMORY MAPPING [ ARRAYS – MULTIDIMENSIONAL ]

int a[3][2];
/* a 3 by 2 table */
/* 3 rows and 2 columns */
/* 6 cells of 4 bytes each */
/* caution: never a[3,2] */

Label Address Value

a[0][0] 400 – 403
a[0][1] 404 – 407
a[1][0] 408 – 411
a[1][1] 412 – 415
a[2][0] 416 – 419
a[2][1] 420 – 4230 0 0 1

1 0 1 1

2 0 2 1

0
1
2

0 1

C stores arrays in row-major order, with row 0 first, then row 1, and so forth.
(sort of …. )

MEMORY MAPPING [ ARRAYS – MULTIDIMENSIONAL ]

int a[3][2];
/* a 3 by 2 table */

a[0][1] = 7;
a[1][0] = 13;

Label Address Value

a[0][0] 400 – 403
a[0][1] 404 – 407 7
a[1][0] 408 – 411 13
a[1][1] 412 – 415
a[2][0] 416 – 419
a[2][1] 420 – 423(7)

(13)
0
1
2

0 1

MEMORY MAPPING [ ARRAYS – THREE DIMENSIONAL ]

int b[2][3][4];
/* a 2 by 3 by 4 table */
/* 2 layers 3 rows 4 columns */
/* 24 cells of 4 bytes each */

Label Address Value Label Address Value

b[0][0][0] 400 – 403 b[1][0][0] 448 – 451
b[0][0][1] 404 – 407 b[1][0][1] 452 – 455
b[0][0][2] 408 – 411 b[1][0][2] 456 – 459
b[0][0][3] 412 – 415 b[1][0][3] 460 – 463
b[0][1][0] 416 – 419 b[1][1][0] 464 – 467
b[0][1][1] 420 – 423 b[1][1][1] 468 – 471
b[0][1][2] 424 – 427 b[1][1][2] 472 – 475
b[0][1][3] 428 – 431 b[1][1][3] 476 – 479
b[0][2][0] 432 – 435 b[1][2][0] 480 – 483
b[0][2][1] 436 – 439 b[1][2][1] 484 – 485
b[0][2][2] 440 – 443 b[1][2][2] 488 – 491
b[0][2][3] 444 – 447 b[1][2][3] 492 – 495

000 001 002 003

010 011 012 013

020 021 022 023

100 101 102 103

110 111 112 113

120 121 122 123

0
1
2

0 1 2 3

MEMORY MAPPING [ ARRAYS – THREE DIMENSIONAL ]

int b[2][3][4];
/* a 2 by 3 by 4 table */

b[0] [2] [0] = 7;
b[1] [0] [2] = 13;

Label Address Value Label Address Value

b[0][0][0] 400 – 403 b[1][0][0] 448 – 451
b[0][0][1] 404 – 407 b[1][0][1] 452 – 455
b[0][0][2] 408 – 411 b[1][0][2] 456 – 459 13
b[0][0][3] 412 – 415 b[1][0][3] 460 – 463
b[0][1][0] 416 – 419 b[1][1][0] 464 – 467
b[0][1][1] 420 – 423 b[1][1][1] 468 – 471
b[0][1][2] 424 – 427 b[1][1][2] 472 – 475
b[0][1][3] 428 – 431 b[1][1][3] 476 – 479
b[0][2][0] 432 – 435 7 b[1][2][0] 480 – 483
b[0][2][1] 436 – 439 b[1][2][1] 484 – 485
b[0][2][2] 440 – 443 b[1][2][2] 488 – 491
b[0][2][3] 444 – 447 b[1][2][3] 492 – 495

000 001 002 003

010 011 012 013

(7) 021 022 023

100 101 13 103

110 111 112 113

120 121 122 123

0
1
2

0 1 2 3

37 38

39 40

MEMORY MAPPING [ VARIABLE LENGTH ARRAYS ]

int n = 3;
int a[n+1];
/* int: 4 bytes */ Label Address Value

a[0] 400 – 403
a[1] 404 – 407
a[2] 408 – 411
a[3] 412 – 415

int a[n+1];

ARRAY SIZE DETERMINED AT RUN TIME

Memory Maps

END OF PART 5

MEMORY MAPPING [ STRINGS – A SPECIAL ARRAY OF CHARACTERS ]

char d[8]
/* char: 1 byte */

d[0] = ‘H’
d[1] = ‘e’;
d[2] = ‘l;
d[3] = ‘l;
d[4] = ‘o’;
d[5] = ‘\0’;

Label Address Value

d[0] 400 H
d[1] 401 e
d[2] 402 l
d[3] 403 l
d[4] 404 o
d[5] 405 \0
d[6] 406
d[7] 407

char d[8];

ARRAY OF CHARACTERS IS NOT A STRING
-> until ‘\0’ is assigned (the NULL character)

STRINGS:
(array of char : terminated with null)

MEMORY MAPPING [ STRINGS – A SPECIAL ARRAY OF CHARACTERS ]

char d[8] = “Magic”;
/* char: 1 byte */

Label Address Value

d[0] 400 M
d[1] 401 a
d[2] 402 g
d[3] 403 i
d[4] 404 c
d[5] 405 \0
d[6] 406 0
d[7] 407 0

char d[8];

STRING ARRAY assigned a VALUE

STRINGS:
(when assigned within quotes
automatically terminated with null)

STRINGS (SIZE):
(the size of the string at d is: 5
– not 8.

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