Numeric types (double, single, integer) in MATLAB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of mixed numeric type operations

What is the output of this MATLAB code?

a = single(5.5); b = int32(2); c = a + b; disp(class(c)); disp(c);

MATLAB

a = single(5.5);
b = int32(2);
c = a + b;
disp(class(c));
disp(c);

A

int32
7

B

double
7.5

C

single
7.5

D

single
7

💡 Hint

Remember MATLAB converts integer types to single or double when mixed with floating types.

When adding a single and an int32, MATLAB converts the int32 to single before addition. The result is single type with value 7.5.

❓ Predict Output

intermediate

Integer division result type

What is the output of this MATLAB code?

x = int16(7); y = int16(2); z = x / y; disp(class(z)); disp(z);

MATLAB

x = int16(7);
y = int16(2);
z = x / y;
disp(class(z));
disp(z);

A

int32
3

B

double
3.5

C

int16
3

D

single
3.5

💡 Hint

Division of integer types returns double in MATLAB.

In MATLAB, dividing two integer types results in a double type value with floating point division.

🔧 Debug

advanced

Identify the error in numeric type conversion

What error does this MATLAB code produce?

a = int8(130); disp(a);

MATLAB

a = int8(130); disp(a);

A No output, infinite loop

B Error: Value exceeds int8 range

C Warning: Data truncated

D No error, displays -126

💡 Hint

int8 can only store values from -128 to 127.

Assigning 130 to int8 wraps around due to overflow, resulting in -126 without error.

🧠 Conceptual

advanced

Memory size of numeric types

Which numeric type uses the least memory in MATLAB?

A int8

B double

C single

D int32

💡 Hint

Check the number of bytes each type uses.

int8 uses 1 byte, single uses 4 bytes, int32 uses 4 bytes, double uses 8 bytes.

❓ Predict Output

expert

Result of mixed numeric array operations

What is the output of this MATLAB code?

A = single([1.5, 2.5]); B = int16([2, 3]); C = A .* B; disp(class(C)); disp(C);

MATLAB

A = single([1.5, 2.5]);
B = int16([2, 3]);
C = A .* B;
disp(class(C));
disp(C);

A

single
3.0 7.5

B

double
3.0 7.5

C

int16
3 7

D

single
3 7

💡 Hint

Element-wise multiplication with mixed types converts integers to single.

int16 array is converted to single before multiplication, result is single array with values 3.0 and 7.5.

Practice

1. Which numeric type is the default in MATLAB when you create a number like 5 without specifying its type?

easy

A. single

B. uint8

C. int32

D. double

Solution

1. Step 1: Understand MATLAB default numeric type

   By default, MATLAB stores numbers as double precision floating-point values.

2. Step 2: Check the given number type

   The number 5 without any type specification is stored as double.

3. Final Answer:

   double -> Option D

4. Quick Check:

   Default numeric type = double [OK]

Hint: Remember: MATLAB defaults to double unless specified [OK]

Common Mistakes:

• Thinking single is default
• Confusing integer types as default
• Assuming uint8 is default

2. Which of the following is the correct way to create a single precision number with value 3.14 in MATLAB?

easy

A. x = single(3.14);

B. x = double(3.14);

C. x = int32(3.14);

D. x = single '3.14';

Solution

1. Step 1: Identify correct syntax for single precision

   Use the function single() with a numeric argument to create a single precision number.

2. Step 2: Check each option

   x = single(3.14); uses single(3.14) which is correct syntax. x = double(3.14); creates double, not single. x = int32(3.14); creates integer, which truncates decimals. x = single '3.14'; is invalid syntax.

3. Final Answer:

   x = single(3.14); -> Option A

4. Quick Check:

   Use single() function for single precision [OK]

Hint: Use single() function to convert numbers to single [OK]

Common Mistakes:

• Using double() instead of single()
• Trying to assign string to single
• Using int32 for decimals

3. What will be the output of the following MATLAB code?

x = int8(127); y = x + 1; disp(y);

medium

A. -128

B. 128

C. Error: Overflow

D. 127

Solution

1. Step 1: Understand int8 range

   int8 stores integers from -128 to 127. Adding 1 to 127 causes overflow.

2. Step 2: Check overflow behavior

   In MATLAB, int8 overflow wraps around to the minimum value, so 127 + 1 becomes -128.

3. Final Answer:

   -128 -> Option A

4. Quick Check:

   int8 overflow wraps to -128 [OK]

Hint: int8 max is 127; adding 1 wraps to -128 [OK]

Common Mistakes:

• Expecting 128 (out of range)
• Expecting error on overflow
• Thinking value stays at 127

4. Consider this MATLAB code:

a = single(1.5); b = int16(a); disp(b);

What is the output and why?

medium

A. 1.5

B. 1

C. 2

D. Error: Cannot convert single to int16

Solution

1. Step 1: Convert single to int16 behavior

   When converting from single to int16, MATLAB truncates the decimal part (does not round).

2. Step 2: Apply truncation to 1.5

   Truncating 1.5 results in 1, so b becomes 1.

3. Final Answer:

   1 -> Option B

4. Quick Check:

   Conversion truncates decimals, so 1.5 -> 1 [OK]

Hint: Conversion truncates decimals, no rounding [OK]

Common Mistakes:

• Expecting rounding to 2
• Expecting error on conversion
• Expecting output as 1.5

5. You want to store a large array of numbers between 0 and 255 efficiently in MATLAB. Which numeric type should you choose to minimize memory while preserving all values exactly?

hard

A. double

B. single

C. uint8

D. int16

Solution

1. Step 1: Identify value range and memory needs

   Values are between 0 and 255, so an unsigned 8-bit integer (uint8) fits exactly.

2. Step 2: Compare types for memory and precision

   double and single use more memory and are floating-point. int16 uses 16 bits and allows negative values, wasting space.

3. Step 3: Choose the best type

   uint8 uses 8 bits, stores 0-255 exactly, and saves memory.

4. Final Answer:

   uint8 -> Option C

5. Quick Check:

   Use uint8 for 0-255 integer range to save memory [OK]

Hint: Use uint8 for 0-255 integers to save memory [OK]

Common Mistakes:

• Choosing double wastes memory
• Using int16 wastes space and allows negatives
• Using single loses integer precision