# Parameter
<a name="API_Parameter"></a>

The `Parameter` data type.

## Contents
<a name="API_Parameter_Contents"></a>

 ** ParameterKey **   
The key associated with the parameter. If you don't specify a key and value for a particular parameter, CloudFormation uses the default value that's specified in your template.  
Type: String  
Required: No

 ** ParameterValue **   
The input value associated with the parameter.  
Type: String  
Required: No

 ** ResolvedValue **   
Read-only. The value that corresponds to a Systems Manager parameter key. This field is returned only for Systems Manager parameter types in the template. For more information, see [Specify existing resources at runtime with CloudFormation-supplied parameter types](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/cloudformation-supplied-parameter-types.html) in the * AWS CloudFormation User Guide*.  
Type: String  
Required: No

 ** UsePreviousValue **   
During a stack update, use the existing parameter value that the stack is using for a given parameter key. If you specify `true`, do not specify a parameter value.  
Type: Boolean  
Required: No

## See Also
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For more information about using this API in one of the language-specific AWS SDKs, see the following:
+  [AWS SDK for C\$1\$1](https://docs.aws.amazon.com/goto/SdkForCpp/cloudformation-2010-05-15/Parameter) 
+  [AWS SDK for Java V2](https://docs.aws.amazon.com/goto/SdkForJavaV2/cloudformation-2010-05-15/Parameter) 
+  [AWS SDK for Ruby V3](https://docs.aws.amazon.com/goto/SdkForRubyV3/cloudformation-2010-05-15/Parameter)