CS计算机代考程序代写 Lecture 03

Lecture 03

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ECE 209
Computer Systems Programming
Spring 2021

Lecture 05

Announcements
Z3 was moved to Thursday, 2/18
Program 1 moved to Friday, 2/26
Problem session PS2: 2/17 — CLion!!!
Quiz 2: 2/24

Conditional statement
Iterative statements (loops)

Conditional

Execute statement
if condition is true. T

F

Conditional

Execute statement
if condition is true.

if (expr) statement

0: false
non-zero: true

T

F

if (x > 10) x += 4;

if (x > 10) ;

if (x != 0) {
y = 100;
z = f + g;

}

if (expr) statement

if (x)
y = 100;

if (x)
y = 100;
z = f + g;

if ((x > 10) && (x < 20)) x += 4; if (expr) statement Conditional Execute statement1 if condition is true. Otherwise, execute statement2. T F Conditional Execute statement1 if condition is true. Otherwise, execute statement2. T F if (expr) statement else statement if (x > 10) x += 4;
else x = 10;

if ((x >= 0) && (x <= 100)) { y = 1; z = 2; } else { y = 2; z = 1; } if (expr) statement else statement Multiple Choices... if (x < 10) { printf("Less than 10.\n"); } else if (x <= 20) { printf("Between 10 and 20.\n"); } else { printf("Greater than 20.\n"); } Multiple Choices... if (x < 10) { printf("Less than 10.\n"); } else if (x <= 20) { printf("Between 10 and 20.\n"); } else { printf("Greater than 20.\n"); } if (expr) statement else statement Common Mistakes if (x = 10) printf("Less than 10.\n"); else z = 1; y = 2; // Determine toll based on hour of travel if (timeHour < 6) { // Before 6:00 am tollAmount = 1.55; } else if (timeHour < 10) { // 6 am to 9:59 am tollAmount = 4.65; } else if (timeHour < 18) { // 10 am to 5:59 pm tollAmount = 2.35; } else { // 6 pm and after tollAmount = 1.55; } Conditional statement Iterative statements (loops) Iteration T F As long condition is true, execute statement. Statement will (usually) change something, so that condition eventually becomes false. Iteration T F As long condition is true, execute statement. Statement will (usually) change something, so that condition eventually becomes false. While Loop T F As long condition is true, execute statement. while (expr) statement While Loop T F currPower = 2; userChar = 'y'; while (userChar == 'y') { printf("%d\n", currPower); currPower *= 2; scanf("%d", &userChar); } While Loop T F currPower = 2; scanf("%d",&userInput); while (currPower <= userInput) { currPower *= 2; } printf("%d\n", currPower); Do-While Loop T F Execute statement as long condition is true. do statement while (expr); For Loop T FEvaluate init expression. As long condition is true, execute statement and evaluate re-init expression. for (expr;expr;expr) statement More complex syntax, but fundamentally no different than while loop. For Loop T F for (init;cond;re-init) statement Expressions Typically, init and re-init have side effects. Separated by semicolons. These are not statements!! For Loop T F for (i=0; i<=100; i+=10) { printf("%d\n", i); } For Loop T Fscanf("%d",&n); sum = 0; for (int i = 1; i<=n; i++) { sum += i*i; } printf("%d\n", sum); Can declare a new variable in for-loop, but only visible within the loop. For Loop T FCommon re-init expressions i++ i+1 ++i i >> 1
i += 1
i = i + 1
i += n
i -= n
i >>= 1

The first four are completely equivalent!

WRONG!

Common Mistakes

Using assignment instead of equals.

Forgetting to change condition variable.

Incorrect terminating condition (e.g. off-by-one).

Lecture 05
Slide Number 2
Slide Number 3
Conditional
Conditional
Slide Number 6
Slide Number 7
Conditional
Conditional
Slide Number 10
Multiple Choices…
Multiple Choices…
Common Mistakes
Slide Number 14
Slide Number 15
Iteration
Iteration
While Loop
While Loop
While Loop
Do-While Loop
For Loop
For Loop
For Loop
For Loop
For Loop
Common Mistakes