Research and Advances

Designing computer system messages

tive computer systems and studies of their users, we have become increasingly aware of the importance of system messages. Novice users are unimpressed with CPU speeds, disk storage capabilities, or elegant file structures. For them, the system appears only in the form of the messages on their screens or printers. So when novices encounter violent messages such as “FATAL ERROR, RUN ABORTED”, vague phases like “ILLEGAL CMD”, or obscure codes such as “OC7” or “IEH2191”, they are understandably shaken, confused, dismayed, and discouraged from continuing. The negative image that computer systems sometimes generate is, we believe, largely due to the difficulties users experience when they make mistakes or are unsure about what to do next.
Research and Advances

Control flow and data structure documentation: two experiments

Two experiments were carried out to assess the utility of external documentation aids such as macro flowcharts, pseudocode, data structure diagrams, and data structure descriptions. A 223 line Pascal program which manipulates four arrays was used. The program interactively handles commands that allow the user to manage five lists of items. A comprehension test was given to participants along with varying kinds of external documentation. The results indicate that for this program the data structure information was more helpful than the control flow information, independently of whether textual or graphic formats were used.
Research and Advances

Jump searching: a fast sequential search technique

When sequential file structures must be used and binary searching is not feasible, jump searching becomes an appealing alternative. This paper explores variants of the classic jump searching scheme where the optimum jump size is the square root of the number of records. Multiple level and variable size jump strategies are explored, appropriate applications are discussed and performance is evaluated.
Research and Advances

Experimental investigations of the utility of detailed flowcharts in programming

This paper describes previous research on flowcharts and a series of controlled experiments to test the utility of detailed flowcharts as an aid to program composition, comprehension, debugging, and modification. No statistically significant difference between flowchart and nonflowchart groups has been shown, thereby calling into question the utility of detailed flowcharting. A program of further research is suggested.
Research and Advances

Structured data structures

Programming systems which permit arbitrary linked list structures enable the user to create complicated structures without sufficient protection. Deletions can result in unreachable data elements, and there is no guarantee that additions will be performed properly. To remedy this situation, this paper proposes a Data Structure Description and Manipulation Language which provides for the creation of a restricted class of data structures but ensures the correctness of the program. This is accomplished by an explicit structure declaration facility, a restriction on the permissible operations, and execution-time checks.
Research and Advances

Optimum data base reorganization points

In certain data base organization schemes the cost per access may increase due to structural inefficiencies caused by update. By reorganizing the data base the cost per access may be reduced. However, the high cost of a reorganization prohibits frequent reorganizations. This paper examines strategies for selecting the optimum reorganization points.

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