CompTIA Tech+ (FC0-U71)Software Development ConceptsMedium
A developer is debugging a program where a variable named 'total_sum' occasionally holds an unexpected value that combines a number and a string, for example, '10050' instead of '150' when adding 100 and 50. This behavior suggests that one of the operands might be treated as a string instead of a number during the addition operation. Which programming concept is most likely causing this issue?
- AType declaration
- BType inference
- CType checking
- DType coercion
Show answer & explanationAnswer & explanation
Correct answer: D. Type coercion
Type coercion (or implicit type conversion) occurs when a programming language automatically converts one data type to another. In this case, if one operand is a string and the other is a number, some languages will coerce the number to a string and perform string concatenation instead of numeric addition.
Why the other options are wrong
- A. Type declaration is explicitly stating the data type of a variable.
- B. Type inference is when the compiler/interpreter automatically deduces the type of a variable.
- C. Type checking is the process of verifying the data types of variables and expressions to ensure compatibility.
Type Coercion (Implicit Type Conversion)
The automatic or implicit conversion of values from one data type to another by a programming language during an operation. This can sometimes lead to unexpected results if not understood.
- Happens automatically, without explicit instruction from the programmer.
- Common in dynamically typed languages like JavaScript or Python.
- Can lead to errors like '1' + 2 resulting in '12' instead of 3.
- Explicit conversion (casting) is generally preferred for clarity and control.
Memory trick: Coercion is when types 'co-operate' on their own, sometimes badly.