# Timer 555 Calculator Pro vs Z80CPM

The clearest difference is price: Z80CPM at Free against Timer 555 Calculator Pro's $0.99. Z80CPM also leads on update cadence (every 10 days vs every 3 months) and rating (5.0 vs 4.7). Timer 555 Calculator Pro's advantage is iOS requirement (13.2 vs 15.0). On ratings volume, ads, in-app purchases and device support there is nothing between them.

Z80CPM is free to download; Timer 555 Calculator Pro costs $0.99 up front. Neither carries in-app purchases, so what you see is what you pay.

Z80CPM holds the better App Store score, 5.0 against 4.7. Both are backed by a comparable volume of ratings — 3 and 2 respectively.

Timer 555 Calculator Pro ships an update every 3 months, Z80CPM every 10 days. The most recent releases landed on October 23, 2026 and October 5, 2026 respectively.

## The numbers

| Metric | Timer 555 Calculator Pro | Z80CPM |
| --- | --- | --- |
| Price | $0.99 | **Free** |
| Rating | [4.7 (3 ratings)](https://appshunter.io/ios/app/timer-555-calculator-pro/id833443125/reviews) | **[5.0 (2 ratings)](https://appshunter.io/ios/app/z80cpm/id6756590871/reviews)** |
| Number of ratings | **3** | 2 |
| Positive reviews | 100.0% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 3 months | **Every 10 days** |
| Monetization | Paid | **Free** |
| Size | 3 MB | 1 MB |
| Requires iOS | **13.2** | 15.0 |
| Devices | iPhone, iPad, iPod | **iPhone, iPad, iPod, Mac** |
| Age rating | 4+ | 4+ |
| Developer | [Siu Yuen Ho](https://appshunter.io/developer/814088527) | [Aaron Wohl](https://appshunter.io/developer/1860336063) |

## What reviewers say

### Timer 555 Calculator Pro

[App page](https://appshunter.io/ios/app/timer-555-calculator-pro/id833443125)

Calculate parameters for monostable and astable circuits. Find component combinations for desired pulse width or frequency. Share circuit files via iCloud Drive or AirDrop.

**Highlights:** Calculate monostable pulse width, Calculate astable frequency, Find component combinations, Adjust component tolerance, Unlimited combinations (Pro), Share circuit files

**In-app purchases:** none


### Z80CPM

[App page](https://appshunter.io/ios/app/z80cpm/id6756590871)

Experience the classic CP/M operating system on your iOS or Mac device with a full Z80 processor emulator. Run authentic CP/M software, including operating systems, word processors, programming languages, and text adventures. Works offline with support for multiple disk images.

**Highlights:** Full Z80 emulation, VT100 terminal support, Multiple disk image mounting, Offline functionality, Native Mac support, Downloadable CP/M disk images

**Features:** Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is Timer 555 Calculator Pro free?

Timer 555 Calculator Pro costs $0.99, with no in-app purchases.

### Is Z80CPM free?

Z80CPM is free to download, with no in-app purchases.

### Which has better reviews, Timer 555 Calculator Pro or Z80CPM?

Z80CPM is rated higher. Timer 555 Calculator Pro averages 4.7 out of 5 from 3 ratings, while Z80CPM averages 5.0 from 2 ratings.

### Do Timer 555 Calculator Pro or Z80CPM have ads?

Neither Timer 555 Calculator Pro nor Z80CPM shows ads.

### Which is updated more often, Timer 555 Calculator Pro or Z80CPM?

Timer 555 Calculator Pro ships an update every 3 months, and Z80CPM every 10 days. Most recently, Timer 555 Calculator Pro was updated on October 23, 2026 and Z80CPM on October 5, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*