Information Technology • Project Management

Critical Path

Tasks

0 days = a milestone

The project's schedule

What if?

0 days longer

Critical Path — Explanation

A project is a set of tasks (activities). Each takes a time (its duration) and some can't start until others have finished (its dependencies, or predecessors). Tasks that don't depend on each other can run at the same time, so the project takes less time than all the durations added up.

How to use it. Choose a preset, or edit the tasks on the left: a name, a duration in days, the letters of the tasks it depends on (e.g. B, C) and how many people it needs. Switch between the Gantt chart, the network and the table of times in the title bar. Use What if? to make one task take longer, and drag a bar on the Gantt chart to start a task later.

Critical path analysis (CPA)

The diagrams

Resources and project management tools

Common exam mistakes: adding up every duration for the project length (tasks in parallel overlap); taking the earliest EF of the predecessors in the forward pass, instead of the latest; forgetting that a task with float still delays the project once the delay is bigger than its float; saying the critical path is the path with the most tasks (it's the one with the longest total time); and drawing a milestone with a duration.

Objective: Cambridge International A Level Information Technology (9626), project management: the stages of a project, project management tools and software, Gantt charts, PERT charts and critical path analysis, including milestones, float and resources.

Where this fits

  • Cambridge: Cambridge A Level Information Technology (9626)
  • NCEA Level 2 Digital Technologies: 91897 Use advanced processes to develop a digital technologies outcome Goes beyond 91897: Float and critical-path calculations go further than 91897, which asks for a planned schedule of tasks and milestones.
  • NCEA Level 3 Digital Technologies: 91907 Use complex processes to develop a digital technologies outcome Goes beyond 91907: Float and critical-path calculations go further than 91907 needs; it asks for scheduling within a recognised method.
  • NCEA Level 3 Mathematics: 91576 Use critical path analysis in solving problems
  • Pearson Edexcel International: Edexcel International A Level Information Technology; Edexcel International A Level Mathematics

Critical Path — Key Terms

Key concepts in English, with te reo Māori, Chinese (Simplified) and Korean.

EnglishTe reo Māori中文（简体）한국어What it means on this page
Gantt Chartno attested term甘特图 (gāntètú)간트 차트 (ganteu chateu)A bar chart of a project's schedule: one bar for each task, from its start to its finish, along a timeline.
PERT Chartno attested termPERT 图 (PERT tú)PERT 차트 (PERT chateu)A network diagram of a project: the tasks and arrows showing which must finish before another can start.
Critical Path Analysis (CPA)no attested term关键路径分析 (guānjiàn lùjìng fēnxī)주경로 분석 (jugyeongno bunseok)Working out each task's earliest and latest start and finish times (the forward and backward passes) to find the critical path and each task's float.
Critical Pathno attested term关键路径 (guānjiàn lùjìng)주경로 (jugyeongno)The longest chain of dependent tasks through a project. Its tasks have no float, so a delay to any of them delays the whole project.
Dependencyno attested term依赖关系 (yīlài guānxì)의존 관계 (uijon gwangye)A task that must be finished before another task can start (a predecessor).
Durationno attested term工期 (gōngqī)소요 기간 (soyo gigan)How long a task takes, for example in days.
Earliest Start (ES)no attested term最早开始时间 (zuìzǎo kāishǐ shíjiān)가장 빠른 시작 시간 (gajang ppareun sijak sigan)The soonest a task can start: the latest earliest finish of the tasks it depends on.
Latest Start (LS)no attested term最迟开始时间 (zuìchí kāishǐ shíjiān)가장 늦은 시작 시간 (gajang neujeun sijak sigan)The latest a task can start without delaying the project: its latest finish minus its duration.
Floatno attested term浮动时间 (fúdòng shíjiān)여유 시간 (yeoyu sigan)How long a task can be delayed without delaying the whole project: latest start minus earliest start. Also called slack.
Milestoneno attested term里程碑 (lǐchéngbēi)마일스톤 (mailseuton)A point in a project that marks the end of a stage or a deliverable. It takes no time (a duration of 0).
Resourceno attested term资源 (zīyuán)자원 (jawon)Something a task needs: people, equipment, materials, time or money.
Resource Levellingno attested term资源平衡 (zīyuán pínghéng)자원 평준화 (jawon pyeongjunhwa)Moving tasks within their float to even out the resources needed each day, without delaying the project.
Project Management Softwareno attested term项目管理软件 (xiàngmù guǎnlǐ ruǎnjiàn)프로젝트 관리 소프트웨어 (peurojekteu gwalli sopeuteuweeo)Software that helps plan and run a project: scheduling, Gantt and PERT charts, allocating resources, budgets, sharing documents and tracking progress.
Project Life Cycleno attested term项目生命周期 (xiàngmù shēngmìng zhōuqī)프로젝트 생명주기 (peurojekteu saengmyeongjugi)The stages of a project: initiation, planning, execution, monitoring and control, and closure.

On the te reo Māori column. Terms marked as gaps have no attested equivalent in the sources checked — Karaitiana Taiuru's Dictionary of Māori Computer and Social Media Terms, Paekupu, the Reserve Bank's te reo financial glossary, NZQA and Te Aka. No coinage is printed as though it were established; where a class needs one, commission it from Te Taura Whiri i te Reo Māori and credit the translator. Te reo Māori is not italicised and takes no plural "s".