Usability is . 1.the degree to which a program meets the needs of a user, including but not limited to learnability, reliability, and ease of use

2.a testing method that uses a program that tests another program

3.a debugging technique that uses print statements to trace the program flow

4.conforming to accepted standards of behavior

(doing a quiz, need an answer asap please)

Which of the following is true of operations within a spreadsheet program’s built-in functions? a. operations within parentheses, then multiplication and division, and then addition and subtraction are computed. b. operations within parentheses, then addition and subtraction, and then multiplication and division are computed. c. multiplication and division, then addition and subtraction, and then operations within parentheses are computed. d. addition and subtraction, then multiplication and division, and then operations within parentheses are computed

Consider a slotted aloha system, where the time slot equals the fixed duration of each packet. assume that there are 4 stations a,b,c,d sharing the medium. (a) stations a,b,c,d receive one packet each from higher layers at times 1.3, 1.5, 2.6,5.7 respectively. show which transmissions take place when, according to the slottedaloha protocol; describe all transmissions until all four packets have been successful.when needed, each station has access to the following sequence of random number, provided by a random number generator and drawn uniformly between 0 and 1: (1) station a draws numbers: 0.31, 0.27, 0.78, 0.9, 0.9, 0.11, 0. (2) station b draws numbers: 0.45, 0.28, 0.11, 0.83, 0.37, 0.22, 0. (3)station c draws numbers: 0.1, 0.2, 0.3, 0.4, 0. (4) station d draws numbers: 0.36, 0.77, 0.9, 0.1, 0.1, 0.1, 0.1, 0. (b) in slotted aloha, a station transmits in each time slot with a given probability. what probabilities would you assign to each of the four stations so as to: (i) maximize the efficiency of the protocol? (ii) maximize fairness among the four stations? (c) will the efficiency increase or decrease if we modify slotted aloha as follows: (i) get rid of slots and allow stations to transmit immediately? (ii) implement carrier sensing? (iii) implement collision detection? (iv) implement collision avoidance?

The forerunner to cell phones, pdas, and smartphones was