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ZPL, short for Z-level Programming Language, is a high-level programming language designed for single and multi-processor computers. It was developed at the University of Washington in the 1990s to support scientific computations, particularly those involving matrix calculations. ZPL's primary feature is its support for parallel computation, which allows it to execute multiple tasks simultaneously on different processors. It uses an array programming model where operations are performed on whole arrays instead of individual elements. This makes it easier to write efficient code for complex mathematical problems. Despite its power and flexibility, ZPL has a simple syntax that is easy to learn and use.

Ask the right questions secure the right ZPL talent among an increasingly shrinking pool of talent.

First 20 minutes

General ZPL app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in ZPL application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

How would you explain the purpose of ZPL in programming?

ZPL is a programming language used for designing and controlling the print formatting for Zebra printers. It allows developers to customize the print output according to their needs.

What are the basic commands used in ZPL?

The basic commands used in ZPL include ^FO for field origin, ^FD for field data, ^FS for field separator, ^CF for change font, and ^XZ for end format.

How would you define the ^FO command in ZPL?

^FO command in ZPL is used to set the field origin, i.e., the point where the printing will start on the label.

Describe the difference between ^FD and ^FS commands in ZPL.

^FD is used to define the field data, i.e., the actual data to be printed, while ^FS is used as a field separator to indicate the end of the field definition.

What is the use of the ^CF command in ZPL?

^CF command in ZPL is used to change the font settings for any text fields that follow this command.

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What you’re looking for early on

Does the candidate demonstrate a strong understanding of ZPL?

Has the candidate worked on relevant projects in the past?

Is the candidate able to solve complex problems?

Does the candidate show good communication skills?

Next 20 minutes

Specific ZPL development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

How would you use the ^BY command in ZPL?

^BY command in ZPL is used to set the width ratio and height of the barcode. It is followed by the width ratio, width in dots, and height in dots.

What does the ^PQ command do in ZPL?

^PQ command in ZPL is used to specify the quantity of labels to be printed.

How would you use ZPL to print a barcode on a label?

To print a barcode on a label, you would use the ^BC command followed by the barcode parameters, then use the ^FD command to define the barcode data, and finally use ^FS to end the field.

What is the purpose of the ^XA and ^XZ commands in ZPL?

^XA and ^XZ commands in ZPL are used to start and end a label format respectively. All the commands between ^XA and ^XZ define the label format.

How would you use ZPL to print a label with text and a barcode?

First, use the ^XA command to start the label format. Use ^FO to set the field origin, ^A to set the font, ^FD to define the text, and ^FS to end the field. Then use ^BY to set the barcode size, ^BC to define the barcode, ^FD to define the barcode data, and ^FS to end the field. Finally, use ^XZ to end the label format.

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At this point, a skilled ZPL engineer should demonstrate strong problem-solving abilities, proficiency in ZPL programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with ZPL.

What does the following ZPL code do?
^XA
^FO50,50
^ADN,36,20
^FDHello, World!^FS
^XZ
This ZPL code prints a text 'Hello, World!' on a label at position (50,50).
What will be the output of the following ZPL code?
^XA
^FO50,50
^BCN,100,Y,N,N
^FD123456^FS
^XZ
This ZPL code will print a Code 128 barcode with the data '123456' on a label at position (50,50).
What does the following ZPL code do?
^XA
^FO50,50
^BQN,2,10
^FDMM,AAC-42^FS
^XZ
This ZPL code will print a QR code with the data 'AAC-42' on a label at position (50,50).
What will be the output of the following ZPL code?
^XA
^FO50,50
^A0N,50,50
^FDZebra^FS
^FO50,100
^A0N,50,50
^FDProgramming^FS
^XZ
This ZPL code will print two lines of text 'Zebra' and 'Programming' in Arial font on a label at positions (50,50) and (50,100) respectively.

Wrap-up questions

Final candidate for ZPL Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle ZPL application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

How would you print multiple labels with different data using ZPL?

To print multiple labels with different data, you would create a loop in your program to iterate over the data. For each iteration, you would define a new label format with the ^XA and ^XZ commands and use the ^FD command to insert the data.

Describe the difference between ^A and ^CF commands in ZPL.

^A command in ZPL is used to define the font for a specific text field, while ^CF command is used to change the font settings for all the text fields that follow this command.

How would you create a label with a rectangle and text inside it using ZPL?

To create a label with a rectangle and text inside it, you would use the ^GB command to create the rectangle, then use ^FO to set the field origin inside the rectangle, ^A to set the font, ^FD to define the text, and ^FS to end the field.

ZPL application related

Product Perfect's ZPL development capabilities

Beyond hiring for your ZPL engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in ZPL projects, and can engage in multiple capacities.

ZPL Consultive assessments

ZPL Application Conversion Assessment ZPL Application Integration Assessment ZPL Data & Database Integration Assessment

Custom ZPL development projects

Custom ZPL App Conversion ZPL Custom App Development Process App UI Design for ZPL Facelifts

Hiring guide for ZPL Engineers

ZPL Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

What you’re looking to see on the ZPL engineer at this point.

ZPL Consultive assessments

Custom ZPL development projects