An expert-level exam tips and analysis guide for Cambridge International AS Level Computer Science (9618). This guide breaks down the strategic pacing of Paper 1 (Theory Fundamentals) and Paper 2 (Fundamental Problem-solving and Programming Skills), highlights the most common syntax and logical traps found in examiner reports, and provides an actionable study plan for earning top-tier marks.
Theoretical Application, Trace & Verification, Algorithm & Design (Structure Chart/Diagrams), Pseudocode Program Construction
评级
ABCDEU
计算器规定
A silent scientific calculator is required where the syllabus permits one. It must NOT be graphical, programmable, or capable of symbolic algebra (CAS), and it must contain no stored programs or notes.
AO1: Knowledge and understanding of computer science principles. (35%)
AO2: Apply knowledge, understanding and skills to show conceptual or practical understanding. (35%)
AO3: Design, write, implement, and document algorithm solutions. (30%)
根据历届试题与评分标准整理（2023–2025）。
计算器程序
Table mode for roots & turning points
Scientific calculator (e.g. Casio fx-991 series)
用途: Tabulate \(y\) across a range of \(x\) to locate sign changes (roots) and approximate maxima/minima.
使用时机: Solving or sketching a function when you want to find where its graph crosses or turns.
步骤
Enter the function in TABLE mode, set the start, end and step, then read where the sign of \(y\) changes or where it peaks.
考试提示: Allowed, but the calculator must be silent, non-graphical, non-programmable and free of stored content; always show the working the mark scheme requires.
Statistics mode (mean, SD & regression)
Scientific calculator (e.g. Casio fx-991 series)
用途: Read the mean \(\bar{x}\) and standard deviation directly, and the gradient/intercept (and \(r\)) of a linear regression for bivariate data.
使用时机: Any data-handling, statistics, or required-practical analysis question.
步骤
Enter the data in STAT mode (1-VAR or A+BX), then recall \(\bar{x}\), \(\sigma\) or the regression coefficients.
考试提示: Allowed, but the calculator must be silent, non-graphical, non-programmable and free of stored content; always show the working the mark scheme requires.
Carry exact values with Ans & memory
Scientific calculator (e.g. Casio fx-991 series)
用途: Keep full-precision intermediate values to avoid rounding errors.
使用时机: Multi-step calculations where premature rounding loses the final accuracy mark.
步骤
Use Ans, STO/RCL or the M+ memory to reuse the unrounded result of each step; round only the final answer.
考试提示: Allowed, but the calculator must be silent, non-graphical, non-programmable and free of stored content; always show the working the mark scheme requires.
Equation solver — to CHECK your working
Scientific calculator (e.g. Casio fx-991 series)
用途: Use the built-in EQN/SOLVE mode to verify roots of quadratics or simultaneous equations you have already solved by algebra.
使用时机: As a check only, after solving by hand.
步骤
Enter the coefficients in EQN mode (or use SOLVE) and confirm they match your worked solution.
考试提示: Allowed, but the calculator must be silent, non-graphical, non-programmable and free of stored content; always show the working the mark scheme requires.
常见错误
1high涉及分数: 2Information representation
Using bit-depth calculations directly as bytes in graphic resolution calculations, resulting in a size off by a factor of 8.
如何避免: Always divide the bit-depth by 8 first to yield bytes before multiplying by the total resolution to calculate image storage sizes.
2high涉及分数: 1Programming
Omitting quotation marks when specifying literal filenames inside sequential text file pseudocode commands like OPENFILE.
如何避免: Ensure all literal filenames are surrounded by quotation marks, for example: OPENFILE "Stock.txt" FOR READ.
3medium涉及分数: 2Algorithm Design and Problem-solving
Substituting output commands (OUTPUT) inside a standard pseudocode function instead of using the RETURN statement.
如何避免: Check the module specification: if it is a FUNCTION, it must use RETURN to send the output value back to the calling process.
4medium涉及分数: 1Databases
Declaring primary identifiers that have leading zeros (like CustomerID '0123') as integer types in SQL CREATE TABLE.
如何避免: Use CHAR or VARCHAR string types for codes or identifiers that require structural leading zeros to preserve the exact digit length.
5high涉及分数: 3Programming
Failing to write required loop index or boolean structure end indicators such as ENDIF or ENDWHILE in programming blocks.
如何避免: Always close every selection and iteration block explicitly to maintain pseudocode structural integrity and preserve structural marks.
6medium涉及分数: 1Data Types and Structures
Confusing index 0 and index 1 bounds when setting up loops to search or process standard declared arrays.
如何避免: Carefully check the array bounds declaration in the scenario (e.g. ARRAY[1:200]). Start your loop index counter from 1 instead of 0 if defined as such.
7medium涉及分数: 2Programming
Failing to convert boolean or integer fields to strings using NUM_TO_STR() before writing them into sequential text files.
如何避免: Explicitly wrap non-string variables in the NUM_TO_STR() conversion function when concatenating or writing to sequential text files.